The freeway is the subject of ongoing controversy and federal investigation due to a proposed expansion project in Harris County, which would displace hundreds of people from their homes and worsen air quality.

[10] The section north of the curve near SH 3/Monroe Road in southeastern Houston was built on the right-of-way of the former Galveston–Houston Electric Railway, which entered downtown on Pierce Street.

[13] The Gulf Freeway generally parallels SH 3 (old US 75) about one mile (1.6 km) to the west, bypassing La Marque, Dickinson, and South Houston.

As such, when ice storms hit the Dallas area (usually on average one to two times per year), the freeway is shut down, and traffic is diverted to SH 310 and US 175, which parallel I-45.

The more direct route followed by I-45 was not initially part of the system between Richland and Huntsville;[16][17] this cutoff was added by 1919 as SH 32,[18] and US 75 was assigned to the alignment in 1926.

[19] Prior to the coming of the Interstate Highway System in the late 1950s, the only improvements to US 75 in Texas beyond building a two-lane paved roadway were in the Houston and Dallas areas.

[citation needed] Plans made in October 1943, when the Texas Transportation Commission signed an agreement with Houston and Harris County, referred to the new bypass as a relocation of US 75.

Drawings were released by the state on January 31, 1946, and included almost continuous frontage roads, broken only at railroad crossings.

[citation needed] The first freeway dedication in the state took place at 7:00 pm on September 30, 1948, at the overpass over Calhoun Road by the University of Houston.

The roadway between Downtown and Telephone Road was opened to traffic after speeches but lacked an official name, being called the "Interurban Expressway", after the rail line that it replaced, by the press.

Mayor Holcombe quickly started a contest to assign a name, and the city chose the winning entry on December 17, 1948.

The freeway was extended to Griggs Road in February 1951 and Reveille Street (onto which SH 35 was realigned) in July 1951 and was completed to the Galveston Causeway on August 2, 1952, with a ceremony on the bridge over FM 517 near Dickinson.

After the new US 75 was completed, the old road between Downtown and South Houston was dropped from the state highway system, while the remainder became SH 3, connecting to the Gulf Freeway via Winkler Drive, effective August 20, 1952.

[28] The first major change was made in preparation for the North Freeway connection, when the directions of Calhoun Avenue and Jefferson Street were swapped so that they would alternate.

Southeast of Downtown, the at-grade intersections proved dangerous, and only two had been replaced with interchanges by 1959, when the Texas Highway Department began a program to upgrade the road to full freeway standards.

Heavy congestion began to affect the freeway by the early 1960s; two roughly parallel freeways—the Harrisburg and Alvin freeways—were proposed at that time to relieve the traffic but were not built.

[32] That year also marked the end of the reconstruction inside I-610, along with the elevated distribution lanes alongside the mainlanes near Downtown; the first short piece of the Alvin Freeway was finally connected to these in 1999.

Phase two, planned to begin in mid-2012, will be the reconstruction of the frontage roads from just south of FM 1959 to the southern end of the project.

The southbound onramp from Allen Parkway will be moved to enter on the right side, and long-range plans call for the demolition of the outdated Pierce Elevated, with the reroute of I-45 being along I-69/US 59 and I-10/US 90 to the North Freeway.

As of 2018[update], there are no plans to place the Pierce Elevated in a tunnel similar to Spur 366 in Dallas since Greater Houston is prone to flooding, especially in the aftermath of Hurricane Harvey.

This section was opened on December 12, 1955, and allowed US 75 to bypass its run on Main Street;[30] it included interchanges with Allen Parkway and Memorial Drive.

The next piece near downtown opened on July 24, 1962, leaving the 1955 freeway in the Allen Parkway interchange, passing east of Houston Avenue, and connected to an already-built portion at I-610.

This portion opened on August 18, 1967, connecting the Gulf and North Freeways and bypassing the "four-street distribution system", which remains in its original form to this day.

[20] Construction is now complete between FM 1488 to the Walker County line near milepost 100 just south of the northbound truck weigh station and New Waverly, near SH 75 (exit 98).

This project has generated major controversy, with proponents claiming it would "enhance safety and mobility", while opponents point out that it would worsen air quality and greenhouse gas emissions, displace hundreds of people, and fail to meaningfully address congestion.

[4] Among others, the expansion has been opposed by U.S. Representative Sheila Jackson Lee and Harris County Judge Lina Hidalgo.

The highway expansion would displace around a thousand residents, including 919 units in 16 apartment complexes, 160 single-family homes, five places of worship, and two schools.

[citation needed] The final piece of I-45 between the cities opened on October 13, 1971, for 12 miles (19 km) between Fairfield and Streetman.

The stretch through downtown, however, ran along the surface, as did the part south of the bridge over the Trinity River, due to diversion of funds to the north portion.

[48] At the north end, before it merged into the Central Expressway (which continued to carry US 75), I-345 straddled the bridges over Bryan Street and Ross Avenue, the latter the location of the opening ceremonies in 1949.