[3] The highway splits into I-35E and I-35W in two separate places, the Dallas–Fort Worth metroplex in Texas and at the Minnesota twin cities of Minneapolis–Saint Paul.

I-35's southern terminus is the traffic signal at Hidalgo Street in Laredo, Texas, just short of the Mexican border.

The official milemarkers, along with the route of US 77, follow I-35E through Dallas—I-35W, which is 85 miles (137 km) in length, carries its own mileage from Hillsboro to Denton, as though it were an I-35 loop.

After passing through Dallas and Fort Worth, I-35's two forks rejoin each other in Denton near the University of North Texas campus.

In Oklahoma, I-35 runs from the Red River at the Texas border to the Kansas state line near Braman.

It derives its name from the four major cities nearest the intersection: Burlington, Emporia, Topeka, and Ottawa.

I-35 enters Missouri two miles (3.2 km) southwest of Kansas City's Central Business District as a six-lane highway.

Along the north edge of the loop, I-35 joins with I-70 immediately west of Broadway and carries six lanes of traffic with a speed limit of 45 mph (72 km/h).

On I-35E in Minnesota between MN 5 and I-94, in both directions, trucks weighing more than 9,000 pounds (4,100 kg) are banned from the freeway, and the speed limit drops to 45 mph (72 km/h).

This section was not completed until the late 1980s (although the route was cleared and graded earlier) due to opposition from the historic Crocus Hill neighborhood, which sits only a few hundred feet from the alignment.

This is in large part due to efforts of the towns of Wynnewood, Paoli, and Wayne, which fought to keep I-35 as close as possible to US 77.

This was successful due to a threat from Governor Henry Bellmon to build a toll road rather than I-35, and legislation preventing state funds for the Interstate from being spent if it were more than one mile (1.6 km) from the U.S.

On September 1, 1965, the alignment was changed to instead parallel US 65 through northern Iowa, which brought the highway much closer to Mason City.

Local farmers objected to their farms being bisected into triangular pieces, and resulting litigation delayed I-35 for several years.

A November 1972 ruling rejected a lawsuit filed by the farmers, and the final segment of I-35 was allowed to proceed, eventually opening in 1975.

It consisted of a 1,200-foot (370 m) wide highway that also carried utilities such as electricity, petroleum, and water as well as railway track and fiberoptic cables.

[14] In July 2007, US Representative Duncan Hunter successfully offered an amendment to House Resolution 3074, the FY2008 Transportation Appropriations Act, prohibiting the use of federal funds for Department of Transportation participation in the activities of the Security and Prosperity Partnership of North America (SPP).

This amendment will provide Congress the opportunity to exercise oversight of the highway, which remains a subject of question and uncertainty, and ensure that our safety and security will not be compromised in order to promote the business interests of our neighbors.

"[15] Fellow Republican Congressman and presidential candidate Ron Paul brought the issue to mainstream prominence during the December 2007 CNN–YouTube GOP debate, where he rejected the concept and also called it the NAFTA Superhighway after the North American Free Trade Agreement and, like Hunter, framed it within the ultimate goal of creating a North American Union.

In 2011, the Texas Legislature formally repealed its authority for the establishment and operation of the Trans-Texas Corridor with the passage of HB 1201.