Interstate 70 (I-70) is an Interstate Highway that is located in the Commonwealth of Pennsylvania in the United States. It runs east to west across the southwest part of Pennsylvania and serves the southern fringe of the Pittsburgh metropolitan area.

About half of this route is concurrent with I-76 on the Pennsylvania Turnpike, which is a toll road. This is the oldest segment of I-70 in Pennsylvania, having been completed in 1940, and is only one of two segments of I-70 that are tolled, with the other being the Kansas Turnpike.

I-70 is one of only a few Interstate Highways to have a traffic signal—in this case, with U.S. Route 30 (US 30) in Breezewood, where it leaves the Pennsylvania Turnpike and heads toward Maryland.

Two segments of I-70 in Pennsylvania are not designed to modern Interstate standards: a 37-mile (60 km) segment from Washington to New Stanton and the aforementioned half-mile (0.80 km) signalized segment in Breezewood.

I-70 enters Pennsylvania from West Virginia, coming into Donegal Township, Washington County. The highway continues northeast as a four-lane freeway with a standard-size median up to Interstate Highway standards through rural areas of woodland and farmland, coming to its first junction at a partial cloverleaf interchange with State Route 3023 (SR 3023), to the southeast of unincorporated village of West Alexander.

Past this junction, the freeway begins to parallel US 40 on the northwest side of the road, before it enters a series of winding curves. From here, I-70 heads east to meet a weigh station and a welcome center in the eastbound direction, as well as an interchange with SR 3024 connecting to Pennsylvania Route 231 (PA 231) via US 40 in the borough of Claysville.

The freeway curves to a more east-northeasterly direction, where it briefly passes through the borough limits of Claysville, before briefly reentering Donegal Township. I-70 enters Buffalo Township, where it soon meets a pair of right-in/right-out ramps connecting to PA 221, which serves the unincorporated village of Taylorstown to the northeast, in adjacent Blaine Township. The freeway comes into North Franklin Township before crossing into Canton Township at its partial interchange with US 40 which lacks a westbound entrance; the interchange is adjacent to the Washington Crown Center shopping mall located to the southwest of the interchange.

From here, I-70 crosses over an abandoned portion of the Allegheny Valley Railroad's W&P Subdivision line and enters mixed areas of development on the outskirts of the city of Washington, which is also the county seat of Washington County. After passing through an interchange with Sheffield Avenue serving the industrial and commercial area of Jessop Place, the freeway enters the city limits of Washington, where it comes to a pair of right-in/right-out ramps that connect to PA 18. A short distance later, I-70 enters South Strabane Township and reaches its western junction with I-79 at a directional interchange, which heads north toward the city of Pittsburgh.

The freeway turns southeast through the interchange and begins a concurrency with I-79. A Jersey barrier takes over in the highway's median as it comes to a diverging diamond interchange with US 19 in a commercial area surrounded by strip malls.

A short distance later, I-70/I-79 comes to a partial cloverleaf interchange with PA 136 to the northeast of the borough limits of East Washington that provides access to Washington & Jefferson College; a park and ride lot is located in the northeastern corner of the interchange. Past PA 136, the freeway heads back into rural areas with scattered residences, before reaching the eastern split between I-70 and I-79 at a directional interchange.

I-79 turns south toward the city of Morgantown, West Virginia, while I-70 continues east along the original roadway toward the borough of New Stanton in Westmoreland County.

East of I-79, I-70 downgrades to a highway substandard of modern Interstate standards. This section of I-70 (old I-70S) has several dated design features. The median narrows to the point that there are no shoulders between the median barrier and the passing lanes on both sides. On- and off-ramps at many of the interchanges are substandard in both length and geometry, which requires vehicles to decelerate in the travel lanes before entering the off-ramps, and also necessitates the use of stop signs on the on-ramps instead of yield signs. Several overpasses do not meet minimum clearance requirements, which has resulted in damage to and from overheight trucks. Total reconstruction efforts are ongoing that will upgrade most of this segment of I-70 and its interchanges to modern Interstate standards, and various projects are scheduled through the early 2020s.

The first interchange that the freeway meets past I-79 is with PA 519, where the route crosses into Somerset Township. I-70 continues through areas of rural farmland with surroundings of wooded rolling hills and turns to the east-southeast, coming to interchanges with SR 1055 south of the hamlet of Dunningsville and McIllvaine Road southeast of the hamlet of Kammerer, in adjacent Nottingham Township, before reaching the borough limits of Bentleyville at the PA 917 interchange, which only contains an eastbound exit and westbound entrance. Shortly afterward, the freeway crosses over Norfolk Southern Railway's Ellsworth Secondary and meets modified right-in/right-out ramps to Wilson Road, which provides complete access to PA 917 and the center of Bentleyville to and from both directions.

Following Bentleyville, I-70 enters Fallowfield Township, where it has a complete diamond interchange with PA 481, a westbound exit and eastbound entrance to Twin Bridges Road to the northeast of the hamlet of Lover, and a full cloverleaf interchange with the Mon–Fayette Expressway (PA 43), as the route descends into the valley of the Monongahela River. From here, the freeway curves east-northeast into the borough of Twilight, before crossing into the borough of Speers at the interchange with Maple Drive/Twilight Hollow Road.

At this point, I-70 meets PA 88 at a pair of right-in/right-out ramps, prior to crossing over Norfolk Southern Railway's Mon Line, the Monongahela River, and CSX Transportation's Mon Subdivision on the Belle Vernon Bridge, where the route leaves both Speers and Washington County.

Beyond the Belle Vernon Bridge, the route enters Westmoreland County within Rostraver Township. Here, it has a partial cloverleaf interchange with PA 906, before it crosses into the borough of North Belle Vernon and interchanges with Fayette Street, to the northeast of the borough center.

From this point, the freeway heads back into Rostraver Township where it meets PA 201 at a partial cloverleaf interchange northeast of the community of Lynnwood-Pricedale that also provides access to PA 837. I-70 continues through wooded areas with nearby development, reaching an interchange with SR 3011 north of the hamlet of Arnold City in adjacent Washington Township, Fayette County, before coming to a cloverleaf interchange with PA 51 as the route begins to enter the valley of the Youghiogheny River.

Past PA 51, the route crosses the Smithton High-Level Bridge over the Youghiogheny River and CSX Transportation's Keystone Subdivision, where it enters South Huntingdon Township. From here, I-70 interchanges with SR 3031 north of the borough of Smithton, PA 31 at cloverleaf to the northwest of the Pittsburgh Renaissance Festival grounds, and SR 3010 to the southeast of the unincorporated village of Yukon, before it comes into Sewickley Township. In this area, the freeway has an interchange with Waltz Mill Road to the south of the borough of Madison, before it passes through Hempfield Township prior to entering New Stanton. Within the borough limits, I-70 has a dumbbell interchange with SR 3089, before it exits the mainline freeway at a trumpet interchange, to come to a toll plaza for the New Stanton interchange on the Pennsylvania Turnpike (I-76).

At this point, the mainline freeway continues east to a cloverleaf junction between US 119 and the southern terminus of PA 66. I-70 itself passes through the toll plaza and comes to another trumpet interchange, where the Interstate merges onto the eastbound turnpike that heads toward the city of Harrisburg, the state capital of Pennsylvania. In the opposite direction, the Pennsylvania Turnpike heads northwest toward Pittsburgh, then becomes the Ohio Turnpike, which continues towards Cleveland.

For 86 miles (138 km) from New Stanton to Breezewood, I-70 shares a concurrency with I-76 along the Pennsylvania Turnpike. I-70 passes through a wind farm in Somerset County and close to the 9/11 Flight 93 National Memorial in Shanksville. It then has an indirect connection to I-99 in Bedford County before reaching the eastern end of its concurrency with the Turnpike in Breezewood.

I-70 splits from the Pennsylvania Turnpike at the Breezewood Interchange in East Providence Township, Bedford County. The turnpike continues east toward Harrisburg and Philadelphia, while I-70 passes through another toll plaza and passes under its own carriageways, before downgrading into another highway substandard of Interstate standards, at a partial trumpet interchange with US 30. Eastbound I-70 merges onto westbound US 30 to form a half-mile (0.80 km) wrong-way concurrency through the community of Breezewood. This section of I-70 is one of the few instances of where an Interstate Highway follows a road that lacks grade separation and includes traffic signals. I-70 follows US 30 west along a five-lane highway with a center turn lane through commercial areas in Breezewood before it splits from US 30 and turns left onto another freeway alignment. US 30, meanwhile, continues west toward the borough of Everett.

Beyond US 30, I-70 heads south and becomes a four-lane freeway that once again conforms to modern Interstate standards. The median widens, before the freeway crosses over its preceding carriageways and under the Pennsylvania Turnpike. Shortly past the turnpike underpass, there is an interchange with South Breezewood Road before I-70 curves to cross Rays Hill, crossing into Fulton County, and coming to a pair of right-in/right-out ramps with the southern terminus of PA 915 in the unincorporated village of Crystal Spring, in Brush Creek Township. The freeway continues through a valley of farmland and comes to an eastbound rest area on the western slope of Town Hill, which the highway crosses at an oblique angle. In the middle of the mountain crossing, I-70 has another pair of right-in/right-out ramps with the northern terminus of PA 643, and then descends along the length of its eastern slope into another rural valley. Within this valley, the freeway enters Union Township, turns generally more southeast and interchanges with the northern terminus of PA 731, east of the unincorporated village of Amaranth.

Past PA 731, I-70 crosses Sideling Hill and comes into Bethel Township. The route heads through forested and mountainous surroundings in the watershed of Tonoloway Creek, before coming to an interchange with the western end of the highway's concurrency with US 522 in the unincorporated town of Warfordsburg. Southbound US 522 merges onto eastbound I-70 and the two routes run concurrent across the Mason–Dixon line into Washington County, Maryland.

Pennsylvania Route 126
Location	Warfordsburg–Breezewood
Existed	1928–1964

Pennsylvania Route 71 Alternate
Location	Washington–New Stanton
Existed	1957–1963

By 1947, I-70's route across Pennsylvania was included in the planned Interstate Highway System. The route from West Virginia split at Washington, with one branch heading northeast to meet the Pennsylvania Turnpike near Pittsburgh and the other heading east, bypassing Pittsburgh to the south (via a planned bypass of PA 71) to the New Stanton interchange. The piece south from the Breezewood interchange into Maryland was also included in the network.

The route between US 30 in Breezewood and US 522 in Warfordsburg was originally known as Pennsylvania Route 126 (PA 126). In 1957, preliminary numbers were assigned; the longer route via Pittsburgh (now I-79 and I-376) became the main line of I-70, while the southern bypass (now I-70) became Interstate 70S (I-70S). The original alignment is now known as Old 126 or Breezewood Road.

The section of present-day I-70 between PA 519 near Washington and New Stanton was built as a four-lane divided highway known as the "Express Highway"; this road was assigned the temporary PA 71 Alternate (PA 71 Alt.) designation in 1957 and would be designated as I-70S following the completion of additional connecting roads in the Interstate Highway System. On July 15, 1960, I-70 was designated onto the Penn-Lincoln Parkway.

A southern extension of I-79 (which had previously only run from Erie south to Pittsburgh) to Charleston, West Virginia, in 1963 resulted in changes to I-70. On February 26, 1964, as part of the formation of I-76 (east of Downtown Pittsburgh), the American Association of State Highway and Transportation Officials (AASHTO) approved a rerouting of I-70 along I-70S. The former I-70 became I-79 from Washington to downtown Pittsburgh and I-76 to and along the Turnpike to New Stanton. This brought the routing of I-70 to its present form.

In 2011, the Pennsylvania Department of Transportation (PennDOT) began preliminary work for a total reconstruction of I-70 between the West Virginia state line and New Stanton. Approximately $500 million will be spent on this 58-mile (93 km) segment of highway in order to improve it to modern Interstate standards, half of which will be spent redesigning eight interchanges. Other planned improvements include six overpass replacements, a new roadbed, a wider median, electronic ITS signage, and widening the I-70/I-79 concurrency in Washington to six lanes.

Two noteworthy interchange projects will occur in conjunction with the I-70/I-79 widening. Underway is a reconfiguration of the east/south split between I-70 and I-79, which will eliminate the one-lane, low-speed loop ramp from I-79 northbound to I-70 westbound, replacing it with a two-lane, high-speed flyover ramp. Preliminary design work has also been completed for a redesigned interchange between I-70/I-79 and Murtland Avenue (US 19), and involves replacing the existing substandard cloverleaf in favor of the first diverging diamond interchange in Pennsylvania.

In September 2024, it was announced at a Pennsylvania Turnpike Commission press conference that a direct connection for I-70 to enter the Pennsylvania Turnpike at Breezewood would be built, finally completing the highway across the state.

County	Location	mi	km	Old exit	New exit	Destinations	Notes
Washington	Donegal Township	0.000	0.000	–	–	I-70 west – Wheeling	Continuation into West Virginia
		0.776	1.249	1	1	West Alexander
		5.648	9.090	2	6	To PA 231 – Claysville
	Buffalo Township	10.964	17.645	3	11	PA 221 – Taylorstown
	North Franklin–Canton township line	14.940	24.044	4	15	US 40 (Chestnut Street)	Access to Washington Crown Center
	Canton Township	16.027	25.793	5	16	Jessop Place
	Washington	16.451	26.475	6	17	PA 18 (Jefferson Avenue)
	South Strabane Township	17.546	28.238	–	18	I-79 north – Pittsburgh	Western end of I-79 overlap; I-79 exit 38
		18.597	29.929	7	19	US 19 (Murtland Avenue)	Diverging diamond interchange
		18.945	30.489	8	20	PA 136 (Beau Street)
		21.083	33.930	–	21	I-79 south – Morgantown	Eastern end of I-79 overlap; I-79 exit 34; also signed for Waynesburg
	Somerset Township	24.643	39.659	9	25	PA 519 – Eighty Four, Glyde
		27.503	44.262	10	27	Dunningsville
		30.592	49.233	11	31	Kammerer
	Somerset Township–Bentleyville line	32.421	52.177	12A	32A	PA 917 – Ginger Hill	Eastbound exit and westbound entrance
	Bentleyville–Fallowfield Township line	32.780	52.754	12B	32B	To PA 917 – Bentleyville, Ginger Hill	Ginger Hill not signed eastbound
	Fallowfield Township	35.201	56.651	13	35	PA 481 – Monongahela, Centerville
		36.396	58.574	14	36	Lover	Westbound exit and eastbound entrance
		37.555– 37.571	60.439– 60.465	15	37	PA Turnpike 43 – California, Pittsburgh	Signed as exits 37A (south) and 37B (north); Brownsville posted on supplemental signage; E-ZPass or toll-by-plate
	Twilight–Speers line	39.877	64.176	16	39	Speers
	Speers	40.248	64.773	17	40	PA 88 – Charleroi, Allenport
Monongahela River		40.697	65.495	Belle Vernon Bridge
Westmoreland	Rostraver Township	40.776	65.623	18	41	PA 906 – Belle Vernon, Monessen
	North Belle Vernon	41.528	66.833	19	42	North Belle Vernon
	Rostraver Township	42.083	67.726	19A	42A	Monessen	Westbound exit only
		42.742	68.787	20	43	PA 201 to PA 837 – Donora, Fayette City	Signed as exits 43A (south) and 43B (north) westbound
		44.216	71.159	21	44	Arnold City
		46.478	74.799	22	46	PA 51 – Uniontown, Pittsburgh	Signed as exits 46A (south) and 46B (north)
	South Huntingdon Township	48.957	78.789	23	49	Smithton
		51.257	82.490	24	51	PA 31 – Mount Pleasant, West Newton	Was a Cloverleaf Interchange Until 2020
		53.203	85.622	25	53	Yukon
	Sewickley Township	53.923	86.781	25A	54	Madison
	New Stanton	56.978	91.697	26	57	New Stanton, Hunker	Rebuilt interchange combining former exits 57B (Hunker) and 57A (New Stanton)
		57.564	92.640	27	58	US 119 / PA Turnpike 66 north – Greensburg, Connellsville, Delmont	Exit number not signed westbound; Delmont not signed eastbound
		57.765	92.964	New Stanton Toll Plaza (western end of closed toll system)
		57.992	93.329	8	75	I-76 west / Penna Turnpike west – Pittsburgh	Western end of I-76/Penna. Tpk. overlap; exit number not signed eastbound; New Stanton Interchange
	Donegal Township	73.292	117.952	9	91	PA 31 / PA 711 – Ligonier, Uniontown	Donegal Interchange
Somerset	Somerset	92.512	148.884	10	110	To US 219 – Somerset, Johnstown	Access via PA 601; Somerset Interchange
	Stonycreek–Allegheny township line	105.302– 106.502	169.467– 171.398	Allegheny Mountain Tunnel
Bedford	Bedford Township	128.102	206.160	11	146	I-99 north / US 220 – Bedford, Altoona	Access via US 220 Bus.; Bedford Interchange
	East Providence Township	144.102	231.910	12	161	I-76 east / Penna Turnpike east – Harrisburg	Eastern end of I-76/Penna. Tpk. overlap; exit number not signed westbound; Breezewood Interchange
		144.402	232.392	Breezewood Toll Plaza (eastern end of closed toll system)
		146.706	236.100	–	–	US 30 east – McConnellsburg	Eastern end of US 30 overlap
				Eastern end of freeway section
		147.000	236.574			US 30 west – Breezewood, Everett	Western end of US 30 overlap
				Western end of freeway section
		148.465	238.931	29	149	To US 30 west – South Breezewood, Everett	Access via S. Breezewood Rd.; no westbound entrance; signed for US 30/Everett westbound, S. Breezewood eastbound
Fulton	Brush Creek Township	150.948	242.927	30	151	PA 915 – Crystal Spring
		155.510	250.269	31	156	PA 643 – Town Hill
	Union Township	163.007	262.334	32	163	PA 731 south – Amaranth
	Bethel Township	167.724	269.926	33	168	US 522 north – Warfordsburg	Western end of US 522 overlap
		170.281	274.041	–	–	I-70 east / US 522 south – Hancock	Continuation into Maryland
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus       Electronic toll collection       Incomplete access

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Interstate 70
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