U.S. Route 190, also known as the Ronald Reagan Memorial Highway, is an east–west United States highway in Louisiana and Texas. It evolved from the shortest of intrastate routes in 1926 to a length comparable to a main Interstate Highway route, leading from the swamps and pine forests of Louisiana to the West Texas desert.

The western terminus is at a point where US 190 intersects with Interstate 10, a few miles east of Bakersfield and 20 mi (32 km) west of the town of Iraan, in the middle of Pecos County. At one time during the 1920s, Iraan was the residence of V.T. Hamlin, the creator of the comic strip Alley Oop.

It runs east through Texas Hill Country speckled with sage brush, intersecting with State Highway 305, crossing into Schleicher County, and intersecting with U.S. Route 277 in Eldorado. Just outside Eldorado was where the raid of the Yearning for Zion Ranch gained national attention. US 190 continues east into Menard County, intersecting State Highway 864, and passing a few miles north of Fort McKavett State Historic Site, entering Menard and intersecting with U.S. Route 83 north a short distance.

Continuing on a northeastward route US 190 enters McCulloch County and into Brady, Texas. Being the closest city to the geographical center of Texas, the city proclaims being the "True Heart of Texas", "where five major highways meet, making it a major gateway to all regions of the state". US 190 enters Brady from the south merging and running concurrent with north U.S. Route 377 and U.S. Route 87 through town, intersecting FM 2028, 2309, then splitting with US 87 and US 377, before exiting the city heading east. US 190 goes through Rochelle, enters San Saba County, through Richland Springs where it intersects FM 45, the communities Algerita, and Harkeyville, and into San Saba, the birth place of actor Tommy Lee Jones, and an intersection with State Highway 16. Continuing east US 190 enters Lampasas County, entering Lometa, merging and running concurrent with U.S. Route 183 south into the city of Lampasas. Splitting from US 183 and continuing east US 190 runs through the town of Kempner entering the extreme southern corner of Coryell County and the city of Copperas Cove. Copperas Cove is located on the southeastern edge of Fort Hood and US 190 traverses through part of the fort, into Bell County and then Killeen. Being directly adjacent to the main cantonment of Fort Hood, both Killeen and Copperas Cove depend on the fort and those stationed there. A restaurant in Killeen was the site of one of the worst mass shootings in U.S. history where 23 people (including the shooter) were killed.

US 190 next intersects and merges with I-35 north through Belton and enters Temple, merging and running concurrent with State Highway 36 south. Continuing east and south US 190 passes through Rogers and enters Milam County then Cameron and merges with U.S. Route 77 south for a distance. A few miles south of Cameron US 190 merges and runs concurrent with U.S. Route 79 north. In Hearne US 190 splits with US 79 and merges running concurrent with State Highway 6 south, entering Brazos County, through Benchley, and into Bryan, that is considered the heart of the Brazos Valley (Southeast Central Texas), and is part of the Bryan-College Station metropolitan area.

US 190 splits with State Highway 6, turning northeast and merging with State Highway 21 north, entering through Kurten, entering Madison County also passing through North Zulch, Cottonwood and into Madisonville, before merging with I-45 south and into Walker County, then entering Huntsville, where US 190 splits heading into Eastern Texas.

Continuing east, US 190 enters San Jacinto County, passing north of Oakhurst and Point Blank, crossing Lake Livingston, entering Polk County and into Onalaska. US 190 from the west makes a semi-loop up over Lake Livingston and down to Livingston, intersecting with US 59 and Business US 59 and through Alabama-Coushatta Indian Reservation, entering Tyler County, merging with FM 256 and into Woodville. East of Woodville FM 256 splits north and US 190 crosses BA Steinhagen Lake, into Jasper County, intersecting with State Highway 63 east, and in the center of Jasper intersecting with U.S. Route 96. Continuing east US 190 travels through Holy Springs enters Newton County, through Farrsville, and into Newton. In Newton US 190 turns south through Bon Weir, and then crosses the Louisiana line.

In Newton County, Texas, US 190 has been designated one of the routes on the Great Texas Coastal Birding Trail. The site number attached to the signs denote the location of the sign. The sign in the picture is located on the westbound side of the highway, inside the Texas line, just west of the "Welcome to Texas" sign near the Sabine River (Texas-Louisiana).

US 190 crosses the Sabine River and enters the western portion of Louisiana in swampy bayou terrain three miles (5 km) west of Merryville, Louisiana. Merryville is the location of the old Coushatta Indian village.

From Merryville the highway heads north by northeast to the community of Junction, Louisiana, also referred to as The Junction. Junction is where LA 111 and US 190 intersect and is the site of a roadside marker and the joining of two Indian trails.

From Junction, US 190 heads east to DeRidder, where it forms a multiplex with US 171 south and passes several NRHP sites such as the Beauregard Parish Jail, Beauregard Parish Courthouse, and the DeRidder Commercial Historic District among others. US 190 runs concurrently with US 171 to Ragley, where US 190 parts with US 171 heading east. From Ragley, the two-lane highway heads nearly due east almost parallel to Interstate 10 until Opelousas. US 190 crosses the northern reach of the Atchafalaya Basin near the Morganza Spillway en route to Baton Rouge. From Baton Rouge, US 190 passes, in places divided, through Denham Springs, Albany, Hammond, Robert, Goodbee, Covington, Mandeville, before reaching the eastern terminus at Slidell (US 11).

The stretch between Interstate 12 south of Covington and the intersection with LA 22 at Mandeville is multilane divided with controlled access. The highway's eastern terminus is in the bayous near Slidell, at an intersection with U.S. Route 90. This junction was once known as the "White Kitchen" after a restaurant that was once located there.

In the original 1926 plan, U.S. 190 served the purpose of modern-day Interstate 12, as the road around the north side of Lake Pontchartrain. The western terminus was in Baton Rouge, Louisiana, meeting U.S. 71 at the Baton Rouge-Port Allen Mississippi River ferry. U.S. 190 followed State Route 7 (in the pre-1955 Louisiana Highway system) east to Covington, then State Route 34 from Covington to Slidell. The original eastern terminus in Slidell was at U.S. 90 (now U.S.11) at the modern intersection of Front Street and Gause Boulevard.

In 1935, the route was extended west across the Mississippi River, ending in the West Texas town of Brady at an intersection with U.S. 87.

U.S. 190 was assigned an additional 150 miles (240 km) across the sparsely-populated area south of San Angelo, Texas in 1979.

The original 1926 route followed the Jefferson Highway through downtown Baton Rouge, then LA 426 (Old Hammond Highway) to the Amite River. East of Baton Rouge, significant differences from the current alignment are as follows: LA 1032 through Denham Springs; LA 1027 into Walker; LA 43 and 1040 (Old Baton Rouge Highway) between Albany and Hammond; South Range Road and LA 1067 (Old Covington Highway) between Hammond and the Tangipahoa River; and U.S. 190 Business through Covington.

West of Baton Rouge, the current alignment generally follows the same route since its extension into Texas in 1935. The only major re-routing was between Deridder and Elton, where the original route followed LA 26. The portion between Oberlin and Elton was re-routed in 1937 to follow U.S. 165 to Kinder before assuming the current alignment between Deridder and Kinder the following year. Other differences from the current route are as follows: LA 110 through Merryville; LA 3099 into DeRidder; LA 3253, 1244, 31, and 742 between Opelousas and Port Barre; Old U.S. 190 between Bayou Courtableau and Krotz Springs and between East Krotz Springs and Lottie; LA 77 between Livonia and Rosedale; and LA 76 between Rosedale and Port Allen.

In 1937, U.S. 190 took over the original route of U.S. 90 from Slidell to the Rigolets Bridge (along current U.S. 11 and LA 433) when that highway assumed its current routing into Mississippi. U.S. 190 was given its current eastern terminus at U.S. 90 in the 1940s, following what is now U.S. 190 Business (Fremaux Avenue) through Slidell until the 1970s when it was shifted onto Gause Boulevard.

In 1951, U.S. 190 was re-routed along U.S. 51 Business (mainline U.S. 51 at the time) and LA 22 between Hammond and Mandeville. The new route passed through Ponchatoula and Madisonville and bypassed Covington. The former route through Covington was restored in 1956.

The current U.S. 190 near Krotz Springs, Louisiana, is an elevated highway. The road was built as a bypass around the road called Old 190 which continues across the Morganza Spillway to the western edge of Lottie. U.S. 190 crosses the Atchafalaya River on two cantilever bridges known as the Krotz Springs Bridge. It crosses the Mississippi River on the 1940-era Huey Long Bridge north of Baton Rouge.

The route is now used as an alternate route for Interstate 10, across the Atchafalaya Expressway. Traffic can be diverted along LA 975 to Krotz Springs, and LA 76 to U.S. 190/LA 1.