U.S. Route 431 (US 431), internally designated by the Alabama Department of Transportation (ALDOT) as State Route 1 (SR 1), is a major north–south state highway across the eastern part of the U.S. state of Alabama. Although US 431's south end is in Dothan, SR 1 continues south for about 13 miles (21 km) along US 231 to the Florida state line.

SR 1 is primarily the unsigned partner route assigned to US 431.The two routes run concurrently from the southern terminus of US 431 at Dothan to the Tennessee state line. South of Dothan, SR 1 is assigned to US 231.

US 231 enters Alabama in Meridianville with US 431. The two routes continue south until it becomes Memorial Parkway. This route is a freeway with Texas U-turns and frontage roads. It junctions with US 72 east. It continues south for about three miles (4.8 km) until it junctions with US 72 west. Immediately after this concurrency terminus, I-565 is featured in another junction as downtown Huntsville rises into view to the east. After a parclo with old SR 20/Clinton Avenue, US 431 loses US 231 at its junction with SR 53. It turns onto Governor's Drive and gains unsigned SR 1. It passes by the hub of the Huntsville Hospital system, which runs throughout North Alabama, and begins its journey across Monte Sano mountain. After leaving the mountain range, it has no more major junctions past this point as it loses the Governor's Drive name. It eventually passes into Marshall County.

After about 20 miles (32 km) of hilly terrain, the route crosses the Tennessee River and enters Guntersville, junctioning with SR 79 north. It continues south and splits into two one-way streets; one for each direction. It junctions with SR 227 and SR 69's termini before losing SR 79 south. It turns almost east-to-west and climbs up Sand Mountain. This grade is so steep that there is a runaway truck ramp northbound. It junctions with SR 205's western terminus and enters Albertville. It junctions with SR 75 and leaves the city, entering Boaz and junctioning with SR 205 and SR 179. It then enters Etowah County at Sardis City.

It descends into Ridgeville and junctions with SR 77 and almost immediately junctions with US 278 west. These junctions are immediately beside a railroad track. US 278 and US 431 travel concurrently to Attalla. They maintain a short concurrency with US 11. US 278 and US 431 leave US 11 and cross under a notable railroad bridge, known for its low clearance. The routes then junction with Interstate 59 (I-59). They immediately enter into Gadsden and junction with SR 211. US 431 and US 278 junction with US 411 and cross a bridge over the Coosa River. The routes junction with George Wallace Drive, which leads to I-759. US 278 leaves US 431 and continues east to Hokes Bluff. US 431 enters Glencoe and crosses into Calhoun County.

The route enters into Wellington and junctions with SR 204. The route then climbs and descends multiple hills as it enters into Alexandria, where it junctions with SR 144. It eventually climbs up a steep hill and gives drivers a great view of Anniston, Cheaha State Park, and some of the highest mountains in Alabama as it descends a steep grade into Anniston. It junctions with SR 21 at another parclo interchange and turns south into Oxford. The route junctions with US 78 and immediately junctions with I-20. The route merges with I-20 and about two miles (3.2 km), it leaves it, turning south, and immediately enters Cleburne County.

The route enters Cheaha State Park, and passes through the forest, junctioning with SR 281, which climbs up to the crest of Mount Cheaha, the highest mountain in the state. It leaves the forest and enters Hollis Crossroads, junctioning with SR 9. It enters Randolph County.

The route has no major junctions until it enters Wedowee. It junctions with SR 48. It leaves Wedowee as a short four-lane divided highway. It regains its two-laned status and eventually enters Roanoke. Here, it junctions with SR 22. It then enters Chambers County.

The route passes through Five Points before crossing into La Fayette. Here, SR 77 returns to the scene as SR 50 has its junction in south La Fayette. In Oak Bowery, US 431 junctions with SR 147. It enters Lee County for about a mile before crossing back into Chambers County. It cuts a corner of Lee County before re-entering into Chambers County for under a mile. It finally enters into Lee County completely, not cutting another corner.

It passes through eastern Opelika before reaching a turn and immediately junctioning with I-85, US 29, and US 280. It gains US 280 and continues along a four-lane divided highway into Russell County.

The two routes run concurrently with US 80 in western Phenix City. It loses US 80 and then leaves US 280 just short of the Georgia line at the Chattahoochee River. In rural Russell County, the route junctions with SR 165. In Seale, it junctions with SR 26. It passes through Pittsview. It then crosses the line into Barbour County.

The route junctions again with SR 165 and crosses a fork of the Chattahoochee River. It enters Eufaula and junctions with US 82 west. Just before the route can cross the river into Georgia, it loses US 82 and moves away from the state line. In rural Barbour County, the route junctions with SR 30, SR 131, and SR 95, also crossing multiple forks of the Chattahoochee River, but not crossing the state line. It crosses the line into Henry County.

It moves farther away from the state line as it enters Abbeville. It junctions with SR 10 and SR 27. It makes the long journey through straight terrain down to Headland. It junctions with SR 134 and leaves the city. It then enters Houston County. The route has entered the Dothan Metropolitan Area.

The route eventually reaches the Ross Clark Circle, which is US 84 at this point. It joins it as it passes through east Dothan. It loses US 84 and continues southwest independently with SR 210, the Ross Clark Circle. It junctions with SR 53 once again as it nears its southern terminus. The beltway turns to the northwest and junctions with US 231 and US 231 Bus. and US 431 Bus., both of which pass through Dothan. SR 1 turns south with US 231, The two business routes end, and US 431 ultimately ends its long journey across east Alabama.

US 431 is a very important route throughout east Alabama, and is traversed by many people alongside US 231 and I-65.

One of the criticisms of US 431 in its entirety from Kentucky to Alabama was that it was mainly a two-lane road. ALDOT has prioritized four-laning the route in Alabama as a viable north–south road corridor in the eastern part of the state.

Of particular concern was the segment from Seale south to the Barbour County line, where rolling hills along the original alignment limit the visibility of oncoming traffic, contributing to poor decisions by motorists to pass, resulting in numerous head-on collisions. In this segment alone, 31 people were killed in crashes between 1992 and 2006, leading Reader's Digest to proclaim it one of "America's Deadliest Highways" in 2000. After being contacted by and subsequently meeting the family of a fatal crash victim in 2003, ALDOT Director Joe McInnes decided to expedite the construction on the last remaining stretch of two-lane road between Seale and the Barbour County line. This 16-mile (26 km) section was completed and opened in late 2010. The old alignment in Russell County is still open to traffic and is now labeled County Route 137.

Traveling south from Tennessee, as of mid-2009, US 431 is a four-lane route to Oxford. Then, after diverting from I-20 east of Oxford at exit 191, it reverts to a two-lane highway southward to Opelika, with a brief four-lane stretch just south of Wedowee. From Opelika southward to its southern terminus in Dothan, US 431 is now open as a four-lane highway.

The Anniston Eastern Bypass, officially named the McClellan Veterans Parkway, is a realigned US 431, two miles (3.2 km) east of downtown Anniston and downtown Oxford. Since the early 1990s, bypasses have been planned on both sides of town to alleviate traffic on Quintard Avenue, the main north–south traffic artery in the region. Despite being planned for years, construction did not begin until after receiving funding in a 2009 economic stimulus bill. Prior to the start of construction, archeological work on part of the route that passed through Fort McClellan located Native American spearpoints and an American Civil War homestead.

The bypass runs from I-20 exit 188 (Leon Smith Parkway), following the Golden Springs Road northwards, and cross the Choccolocco Foothills, then crosses over SR 21/McClellan Boulevard. It is complete from McIntosh Road to where the former alignment of US 431 merged with SR 21 which was resconstructed. The northern portion, which began construction in 2010, is built with two at-grade intersections (McClellan Bypass and Summerall Road) and one trumpet interchange (SR 21/McClellan Boulevard). Much development has been the result of this highway in the past decade along I-20 in Oxford and it is regarded as a way to redevelop McClellan as well as north Anniston.

The total cost of the project was $164 million; the final stretch of the road to be constructed is complete as of December 2015, and work on the US 431 tie-in continued into 2016 before completion. US 431 follows this route from I-20 northward.

County	Location	mi	km	Destinations	Notes
Houston	Dothan	0.000	0.000	US 231 / US 231 Bus. north / US 431 Bus. north (South Oates Street) / SR 210 (Ross Clark Circle) – Ozark, Enterprise, Ashford, Headland, Panama City	Southern end of US 431; SR 1 follows US 231 from this point southward
		12.173	19.591	SR 53 – Cottonwood
		10.442	16.805	US 84 / US 84 Bus. west (SR 12/East Main Street) – Ashford	Southern end of concurrency with US 84
		9.967	16.040	SR 52 – Columbia
		7.062 17.838	11.365 28.707	US 84 / US 431 Bus. (SR 1/Reeves Street) / SR 210 – Ozark, Headland, Eufaula	Northern end of concurrency with SR 210/US 84; SR 1 follows US 431 Bus. through Dothan; southern end of concurrency with SR 1; mileposts switch from SR 210 to SR 1
Henry	Headland	25.754	41.447	SR 134 – Abbeville, Headland, Columbia
		26.270	42.277	SR 173 north – Newville	Southern terminus of SR 173
	Abbeville	39.748	63.968	SR 27 – Ozark, Abbeville
		42.396	68.230	SR 10 – Blue Springs, Abbeville
Barbour	​	59.970	96.512	SR 95 south	Northern terminus of SR 95
	Eufaula	61.908	99.631	SR 131 south – Bakerhill	Northern terminus of SR 131
		64.058	103.091	SR 30 west – Clayton, Troy	Eastern terminus of SR 30
		66.823	107.541	US 82 east (SR 6 east/Barbour Street)	Southern end of concurrency with US 82
		68.307	109.929	US 82 west (SR 6 west) – Montgomery	Northern end of concurrency with US 82
	​	74.949	120.619	SR 165 north / SR 285 – Cottonton	Southern terminus of SR 165/285
Russell	Seale	96.895	155.937	SR 26 west / CR 18 east – Hurtsboro, Union Springs	Eastern terminus of SR 26
		99.105	159.494	SR 169 north / CR 138 east – Phenix City, Seale	Southern terminus of SR 169
	​	109.155	175.668	SR 165 south (Fort Mitchell Road)	Northern terminus of SR 165
	Phenix City	112.081	180.377	US 280 east (SR 38 east) – Birmingham, Opelika, Columbus, Atlanta	Western end of concurrency with US 280
		113.942	183.372	US 80 west (SR 8 west) – Montgomery	Western end of concurrency with US 80
		114.888	184.894	US 80 east (SR 8 east) – Columbus	Eastern end of concurrency with US 80
Lee	Opelika	137.253	220.887	I-85 / US 29 (SR 15) / US 280 west (SR 38 west) – Montgomery, Atlanta	Western end of concurrency with US 280; I-85 Exit 62
Chambers	Waverly	149.840	241.144	SR 147 south – Auburn	Northern terminus of SR 147
	Lafayette	158.859	255.659	SR 50
		160.794	258.773	SR 77 north – Wadley	Southern terminus of SR 77
Randolph	Roanoke	180.783	290.942	SR 22 – Roanoke, Rock Mills
	Wedowee	194.314	312.718	SR 48 west – R. L. Harris Dam	Southern end of concurrency with SR 48
		194.437	312.916	SR 48 east (Woodland Avenue)	Northern end of concurrency with SR 48
Cleburne	Hollis Crossroads	212.540	342.050	SR 9 – Ashland, Montgomery, Atlanta
	​	217.805	350.523	SR 281	SR 281 crosses US 431 on an overpass, but the two routes do not actually intersect. SR 281 is accessible via a county road just south of the overpass.
Calhoun	​	221.328 191.859	356.193 308.767	I-20 east / SR 301 north – Atlanta	I-20 Exit 191/Southern end of I-20 overlap/Southern terminus of SR 301, which follows former alignment of US 431 northward to US 78/mileposts switch from SR-1 to I-20
	Oxford	188.151 225.036	302.800 362.160	I-20 west – Birmingham	I-20 Exit 188/Northern end of I-20 overlap/mileposts switch from I-20 to SR-1
		225.269	362.535	US 78 (SR 4)	Interchange
	Anniston	232.534	374.227	SR 21 (McClellan Boulevard) – Anniston, Jacksonville	Partial cloverleaf/trumpet interchange
	Alexandria	240.300	386.725	SR 144 west – Ohatchee	Eastern terminus of SR 144
	​	247.070	397.621	SR 204 east – Jacksonville	Western terminus of SR 204
Etowah	Gadsden	258.458	415.948	US 278 east (SR 74 east/Piedmont Cut-Off) – Hokes Bluff, Piedmont, Atlanta	Eastern end of concurrency with US 278
		260.232	418.803	SR 291 south (Hood Avenue) to I-759 – Gadsden State Community College	Northern terminus of SR 291
		260.519	419.265	US 411 (SR 25/Albert Rains Boulevard) – Rainbow City, Ashville, Centre	Partial cloverleaf interchange
		261.994	421.638	SR 211 north (North 12th Street)	Southern terminus of SR 211
		265.274	426.917	I-59 – Birmingham, Chattanooga	I-59 Exit 183
	Attalla	266.117	428.274	US 11 north (SR 7 north/3rd Street)	Southern end of concurrency with US 11
		266.449	428.808	US 11 south (SR 7 south/3rd Street)	Northern end of concurrency with US 11
		268.363	431.888	US 278 west (SR 74 west) – Cullman	Western end of concurrency with US 278
		268.829	432.638	SR 77 south – Lincoln, Walnut Grove	Northern terminus of SR 77
	Sardis City	277.880	447.205	SR 205 north	Southern terminus of SR 205
Marshall	Boaz	280.544	451.492	SR 168 (Mill Avenue) – Douglas
	Albertville	286.741	461.465	SR 75 to SR 68 – Geraldine
	Guntersville	292.423	470.609	SR 205 south	Northern terminus of SR 205
		294.742	474.341	SR 79 south – Blountsville, Birmingham	Southern end of concurrency with SR 79
		295.822	476.079	SR 69 south – Cullman, Arab	Northern terminus of SR 69
		296.190	476.672	SR 227 south (Lusk Street) – Lake Guntersville State Park	Northern terminus of SR 227
		302.114	486.205	SR 79 north – Scottsboro	Northern end of concurrency with SR 79
Madison	Huntsville	333.702	537.041	US 231 south (Memorial Parkway) / SR 53 north (Governors Drive) – Arab, Decatur	Southern end of northern concurrency with US 231; southern end of northern signed segment of SR 53
		334.700	538.647	I-565 / US 72 Alt.
		335.207	539.463	US 72 west (SR 2 west) / University Drive	Southern end of concurrency with US 72
		336.884	542.162	US 72 east	Northern end of concurrency with US 72
	Hazel Green	352.958	568.031	US 231 north / US 431 north	Continuation into Tennessee; northern terminus of SR 1
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus

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U.S. Route 431
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