Texas State Highway Loop 1

The first mention of Loop 1 came to public record in 1929. In 1944, the City of Austin Planning Commission (CMAC) proposed the highway be built in parts of the under-utilized right of way owned by the MoPac railroad. Thus, the highway was eventually given the nickname "MoPac" for its proximity to the railroad. The number was originally used for Spur 1 designated on September 26, 1939 from US Highway 90 (US 90) to the Uvalde fish hatchery as a renumbering of SH 3 Spur. This route was cancelled on December 16, 1943. On March 26, 1958, a new route was designated, also called Spur 1, from US 80A to I-10. This route became part of Loop 16 on July 31, 1964, which itself got cancelled on June 26, 1974 when it was transferred to rerouted US 62 and US 85.[1] Loop 1 was first designated on October 27, 1967, from US 290 northward to Farm to Market Road 1325 (FM 1325). On October 24, 1985, the designation was extended southward from US 290 to SH 45.[1]

This table contains the dates of the construction of segments of the road.[6][7][8]

Since 1994, TxDOT has proposed the addition of managed lanes to portions of Loop 1. The MoPac Improvement Project[10] was relaunched in July 2010. In December 2010, four alternative proposals were presented to the public, each of which would add one or more lanes; the "no-build" alternative was also presented. The additions would not increase the right-of-way of the highway, but would be created by reducing the width of existing lanes and reducing and/or eliminating shoulders. An environmental study was completed in August 2012 with a Finding Of No Significant Impact and a recommendation of one new travel lane in each direction, operated as express lanes.[11] Construction began in 2013, and was originally scheduled for completion in September 2015, but by August 2016, the Central Texas Regional Mobility Authority announced further delays.[12] The first of four tolled sections, specifically the northbound toll lane from RM 2222 to Parmer Lane, opened on October 17, 2016. The remainder of the northbound express lane, from Cesar Chavez Street to Parmer Lane, opened on October 7, 2017, and the entire southbound express lane opened on October 28, 2017.

In 2013, the Central Texas Regional Mobility Authority (CTRMA) and TxDOT initiated an environmental study to analyze the best options to improve the MoPac intersections at Slaughter Lane and La Crosse Avenue. In December 2015, the study was completed with a Finding Of No Significant Impact for the project, which allowed it to move forward.[13] The selected design included replacing the at-grade intersection at Slaughter Lane with a diverging diamond interchange[14] and the at-grade intersection at La Crosse Avenue with a diamond interchange. The project broke ground in January 2018 with Webber, LLC as the general contractor.

On August 10, 2018, the existing Slaughter Lane intersection was rerouted to the south.[15] The original intersection was replaced with a bridge over the new Mopac mainlanes. The DDI opened on November 11, 2018, with final completion expected by Spring 2019. The La Crosse Avenue intersection began construction in Fall 2018. On March 29, 2019, the La Crosse Avenue intersection was closed for reconstruction as a bridge.[16] The La Crosse intersection is expected to be completed in 2020. The project as a whole is expected to be completed in 2021.[17]