Southwestern Indiana is an 11-county region of southern Indiana, United States located at the southernmost and westernmost part of the state. As of the 2010 census, the region's combined population is 474,251. Evansville, Indiana's third-largest city, is the primary hub for the region, as well as the primary regional hub for a tri-state area that includes Kentucky and Illinois. Other regional hubs include Jasper, Vincennes, and Washington. Although part of a Midwestern state, this region's culture and language, like much of the rest of Southern Indiana, is somewhat more aligned with that of the neighboring Upland South (such as Kentucky, Tennessee, and Arkansas), rather than the Midwest; the area is Midwest with a Southern influence, rather than Southern with a Midwest influence.

Southwestern Indiana's topography is considerably more varied and complex than most of Indiana, from large tracts of forest, marshes, rolling fields, large flat valleys in the west and south, to several chains of low mountains, high hills, and sharp valleys towards the north and east. Every county in Southwestern Indiana is bounded by a river at one point, whether it be the Wabash River along the west, the Ohio River along the south, the White River, dividing the six northern counties between its two forks, or other smaller rivers. More than 50% of the boundaries of Daviess, Knox, Perry, Posey, and Spencer Counties are dictated by a river or a creek. Just under 50% of Gibson and Pike counties are dictated by a river. About 80% Knox County's boundaries are dictated by either the Wabash or the White River and its West Fork, essentially making the county a river peninsula. Additionally, over half of the area is located within the Wabash Valley seismic zone along with neighboring Southeastern Illinois.

Southwestern Indiana has clusters of separate towns of varying sizes and layouts. Vincennes is laid out in the French quadrangular, while Jasper and Princeton are laid out in a standard grid. Evansville is laid out in both modes of survey, with its downtown being mapped out from the river and the rest of the city being laid out in the standard grid.

Southwestern Indiana, like most of Southern Indiana as a whole contains several of the oldest counties in Indiana, including Knox County, the states's oldest county. In addition, four other area counties; Gibson, Perry, Posey, and Warrick, predate Indiana's statehood and the area also contains Pike County, the first county created after statehood. The youngest county, Martin, was created in January, 1820, was the state's 30th county overall of the states's 92 counties.

In addition to various media definitions, Southwestern Indiana is also defined by most Indiana state agencies, as well as various commercial and economic regions, as an entire area. All of Southwestern Indiana's counties are in Indiana's 8th Congressional District as of 2013. Most of Southwestern Indiana is in the Roman Catholic Diocese of Evansville except for Perry County and Spencer County's Harrison Township, which are in the Archdiocese of Indianapolis. Southwestern Indiana makes up realtor region 12 in Indiana, while nine of the counties make up Economic Growth Region 11 with Daviess and Martin in Region 8.

In addition, the southern third of Southwestern Indiana exists within the Ohio River Valley American Viticultural Area, the second-largest wine appellation in the United States. The Ohio River Valley AVA occupies all of Perry, Posey, Spencer, Vanderburgh, and Warrick Counties, nearly 90% of Gibson County, and portions of Pike and Dubois Counties in Southwestern Indiana.

IN No.	County name	Establishment date (SW Indiana) (history) (statehood)	County seat	Time zone	Population (2015) (rank)	Area sq mi (km) (Rank)	Twps	ZIP code Prefix(es)	% of Boundary by water
14	Daviess	February 2, 1818 (10) (29) (14)	Washington	Eastern	32,906 (6)	437 sq mi (1,130 km) (3)	10	475	55%
19	Dubois	December 20, 1817 (7) (20) (4)	Jasper	Eastern	42,461 (3)	435 sq mi (1,130 km) (4)	12	475	24%
26	Gibson	April 1, 1813 (2) (8) (T)	Princeton	Central	33,775 (5)	526 sq mi (1,360 km) (1)	10	475/476	59%
42	Knox	June 6, 1790 (1) (1) (T)	Vincennes	Eastern	37,927 (4)	516 sq mi (1,340 km) (2)	10	475/478	84%
51	Martin	January 7, 1820 (11) (33) (18)	Shoals	Eastern	10,226 (11)	341 sq mi (880 km) (10)	6	475	18%
62	Perry	November 1, 1814 (4) (12) (T)	Tell City	Central	19,347 (9)	386 sq mi (1,000 km) (8)	7	474/475	52%
63	Pike	December 21, 1816 (6) (16) (1)	Petersburg	Eastern	12,594 (10)	342 sq mi (890 km) (9)	9	475/476	35%
65	Posey	November 11, 1814 (5) (13) (T)	Mt. Vernon	Central	25,512 (7)	429 sq mi (1,110 km) (5)	10	476	63%
74	Spencer	January 10, 1818 (9) (24) (9)	Rockport	Central	20,715 (8)	401 sq mi (1,040 km) (7)	9	475/476	73%
82	Vanderburgh	January 7, 1818 (8) (22) (7)	Evansville	Central	181,877 (1)	236 sq mi (610 km) (11)	8	476/477	26%
87	Warrick	April 30, 1813 (3) (9) (T)	Boonville	Central	61,897 (2)	424 sq mi (1,100 km) (6)	10	475/476/477	19%

(T) - Establishment Date - Indiana Territory County

Name	Primary city or cities	State or states	County or counties	Non-area county or counties influenced	Area	2005 Population
Evansville, IN-KY Metropolitan Statistical Area	Evansville Henderson Princeton	Indiana Kentucky	IN: Gibson, Posey Vanderburgh, Warrick KY: Henderson, Webster	Illinois: Wabash, White Indiana: Spencer Kentucky: Union	2,367 sq mi 6,130 km	352,943

Name	Primary city	State or states	County or counties	Area	2005 Population
Jasper, IN Micropolitan Statistical Area	Jasper	Indiana	Dubois Pike	776 sq mi 2010 km	53,211
Vincennes, IN-IL Micropolitan Statistical Area	Lawrenceville Vincennes	Illinois Indiana	Knox Lawrence	898 sq mi 2,330 km	54,332
Washington, IN Micropolitan Statistical Area	Washington	Indiana	Daviess	437 sq mi 1,130 km	32,200

• As of 2013, all of Southwestern Indiana is in the 8th Congressional District.

County	House District(s)	Senate District(s)	US House District
14 Daviess	45th 63rd 64th	39th 48th	8th
19 Dubois	63rd 73rd 74th	47th 48th	8th
26 Gibson	64th 74th 75th	48th 49th	8th
42 Knox	45th 64th	39th 48th	8th
51 Martin	62nd 63rd	48th	8th
62 Perry	73rd 74th	47th	8th
63 Pike	63rd 64th	48th	8th
65 Posey	76th	49th	8th
74 Spencer	74th 78th	47th	8th
82 Vanderburgh	75th 76th 77th 78th	49th 50th	8th
87 Warrick	75th 77th 78th	47th 50th	8th
Southwestern Indiana	45th 62nd 63rd 64th 73rd 74th 75th 76th 77th 78th	39th 47th 48th 49th 50th	8th

Interstate 64

The older interstate in the region, this stretch of I-64 has been the primary artery of east-west traffic since entering service around 1983. While relatively flat in Posey, Vanderburgh, and Gibson counties, its terrain becomes hillier as it passes through the 25.5-mile (41.0 km) stretch in Warrick County. By the time it approaches U.S. 231, the hills and valleys are sharper, transitioning into the low mountainous conditions found in Perry County as the highway leaves into Crawford County.

Interstate 69

The newer interstate in the region, this stretch of I-69 provides interstate access to Bloomington and Indianapolis. Like I-64, the terrain around Evansville is relatively flat, but becomes hillier in northeastern Gibson County, and becomes progressively hillier through Pike County. The stretch of I-69 in Daviess County between Washington and Elnora is actually flatter than the stretch in Vanderburgh County, while containing some hilly sections south of Washington, but becomes very hilly northeast of Elnora as the highway approaches Crane and leaves the area into Greene County.

U.S. Route 41
US 41 extends from Miami, Florida to the Upper Peninsula of Michigan. This four-lane highway serves the western half of the region. US 41 goes through the city of Evansville, becoming six lanes between the Lloyd Expressway and Diamond Avenue. It bypasses Princeton and Vincennes before continuing north towards Terre Haute.

U.S. Route 50
US 50 extends from Baltimore, Maryland, to Sacramento, California. It is a winding two-lane road in the eastern half of the region which becomes a four-lane road in the western half, near Washington, before joining US 41 in the bypass around Vincennes. It intersects with I-69 just east of Washington. It leaves Indiana on the Red Skelton Bridge.

U.S. Route 150
Coterminous with US 50 from Vincennnes to Shoals, it breaks off and heads eastward while US 50 continues northeast.

U.S. Route 231
This now mostly new four-lane road serves the eastern half of the region. The route is in a process of relocation, as a new four-lane road is under construction from Rockport to Greene County, where it will intersect with Interstate 69.

• April
  • Perry County Dogwood Tour - Perry County, Indiana
• May
  • Gastoff Spring Festival - Montgomery, Indiana
  • Historic Newburgh Wine and Arts Festival - Newburgh, Indiana
  • Spirit of Vincennes Rendezvous - Vincennes, Indiana
• June
  • Spencer County Fair - Grandview, Indiana
  • Haubstadt Somerfest - Haubstadt, Indiana
  • Evansville Freedom Festival - Evansville, Indiana
• July
  • Germania Männerchor Volksfest - Evansville, Indiana
  • Thunder on the Ohio - Evansville, Indiana
  • 4th of July Festival - Otwell, Indiana
  • Gibson County Fair - Princeton, Indiana
  • Cedar Valley Bluegrass Festival - Derby, Indiana
  • Owensville Watermelon Festival - Owensville, Indiana
  • St. Wendel Bierstube - St. Wendel, Indiana
• August
  • Strassenfest - Jasper, Indiana
  • Oakland City Sweetcorn Festival - Oakland City, Indiana
  • Buffalo Trace Festival - Petersburg, Indiana
  • Tell City Schweizer Fest - Tell City, Indiana
  • Knox County Watermelon Festival - Bicknell, Indiana
  • Princeton Golden Heritage Days - Princeton, Indiana
  • Warrick County Fair - Boonville, Indiana
  • Vanderburgh County Fair - Darmstadt, Indiana
• September
  • Princeton Labor Day Celebration Princeton, Indiana
  • Dale Fall Festival - Dale, Indiana
  • Spirit of Vincennes Civil War Days - Vincennes, Indiana
  • Fort Branch Fall Days - Fort Branch, Indiana
  • Bear Hollow Fall Fest & Dasholz - St. Croix, Indiana
  • Gastoff Fall Festival - Montgomery, Indiana
  • Kunstfest - New Harmony, Indiana
  • Poseyville Autumnfest - Poseyville, Indiana
• October
  • West Side Nut Club Fall Festival - Evansville, Indiana
  • Troy Pioneer Days - Troy, Indiana
  • Spencer County Fair Octoberfest - Grandview, Indiana
  • Hoosier Heritage Fall Tour - Perry County, Indiana
  • Cannelton Heritage Festival - Cannelton, Indiana
  • Rome Courthouse Days - Rome, Indiana
  • Historic Newburgh Ghost Walks - Newburgh, Indiana
  • Old Courthouse Catacombs - Old Vanderburgh County Courthouse
• November and December
  • Muster on the Wabash (November) - Vincennes, Indiana (Fort Knox II)
  • Santa Claus Christmas Celebration (December) - Santa Claus, Indiana
  • Numerous Communities have Thanksgiving and Christmas Parades in November and December. There are also numerous Basketball Tournaments that occur in December, including the Gibson County Toyota Teamwork Classic.

From 1966 to 2006, the five southwesternmost counties—Gibson, Posey, Spencer, Vanderburgh, and Warrick—observed Central Daylight Time. The six northern and eastern counties—Daviess, Dubois, Knox, Martin, Perry, and Pike, since 1982—observed year-round Eastern Standard Time as did much of the rest of the state.

In 2006, Indiana Governor Mitch Daniels pushed through legislation for all Indiana counties to observe Daylight Timeon Eastern Time onto Eastern Daylight Time. This action threw both Southwestern and Northwestern Indiana into chaos as counties started to debate whether to return to the Central Time Zone or remain in the Eastern Time Zone and start observing daylight time. This resulted, on April 2, 2006, in all of Southwestern Indiana being in the Central Time Zone.

Not even a month after the change, people began to complain about some of the same problems that people who lived in the original Central Daylight Time counties had been complaining about for years. Most prevalent was the complaint that the Crane Naval Surface Warfare Center had become a "time island". The workers' union of the base subsequently petitioned the Martin County Commissioners to repetition for a change back to Eastern Time. The resulting chain reaction resulted in all of the former Eastern Time counties, along with two Central Time counties, Gibson and Spencer, petitioning for a change to Eastern Time.

On September 20, 2007, after only 15 months and only one winter on Central Time, the DOT returned only five of the eight applicants to the Eastern Time Zone. Gibson, Perry, and Spencer counties did not have enough support to be placed there. However, three of the five counties, Daviess, Knox, and Pike, had little support either, but "convenience of commerce" was given as the reason for their time changes, despite commute patterns into Evansville and the Toyota Motor Manufacturing Indiana plant in Gibson County, the region's largest employer. In Dubois County, a heated disagreement between Huntingburg and Jasper occurred over the topic. Most of Huntingburg's industry and economy is geared towards the Central Time Zone, where Owensboro, Kentucky, and Spencer County, and the Huntingburg area's largest employers, AK Steel and Holiday World, are located. Jasper, though, stated that the majority of its business activity is aimed at the Eastern Seaboard and that returning to the Eastern Time Zone would be in the best interest of the county. The final result was that Daviess, Dubois, Knox, Martin, and Pike counties returned to the Eastern Time Zone on November 4, 2007, once again dividing Southwestern Indiana.

38°30′N 87°0′W / 38.500°N 87.000°W / 38.500; -87.000