Originally, the entire highway was two lanes wide; west of Bonsall, the route was widened in stages, after decades of funding shortages, planning, and litigation.

The California Department of Transportation (Caltrans) maintained plans to expand the entire length of the highway west of I-15 to an expressway, and as of May 2017, construction between Bonsall and I-15 was complete.

[10] The part of the highway from the western terminus to Douglas Drive is also named for Tony Zeppetella, an Oceanside police officer killed while on duty performing a traffic stop in 2003.

[26] The road that extended from US 101 in Oceanside all the way to SR 79 near Lake Henshaw was originally added to the state highway system in 1933,[27] but was not designated as legislative Route 195 until 1935.

[47] In January 1975, Caltrans presented plans to realign SR 76 away from Mission Avenue and move it to the south side of the San Luis Rey River from I-5 to Frontier Drive.

[51] After this, at the start of the next year, the CHC decided to keep the proposal, though there were concerns that construction would be delayed due to the state financial crisis.

[52] Caltrans stated a few months later that SR 76 would be delayed because of the funding issues and the relatively low levels of traffic that would not support building a freeway.

[54] A petition drive began soon after, supported by many North County leaders, with the exception of Bonsall due to concerns about a full freeway running through the community.

[59] In May 1980, the state Assembly Transportation Committee approved a resolution that requested an answer from the governor at the time, Jerry Brown, and Caltrans as to why certain projects, including SR 76, had not been started.

[60] In the meantime, the Oceanside Development Agency recommended that the new highway be extended west to Pacific Street to aid in redeveloping the downtown area.

[61] The San Diego Regional Coastal Commission disagreed with constructing the highway, among other development proposals for downtown Oceanside, due to concerns about destroying habitat along the river and the marsh areas.

[62] Soon after, in October 1980, the California Coastal Commission recommended removing the realignment of the freeway from plans entirely, on environmental grounds.

[68] Caltrans tentatively approved the westernmost 2.5 miles (4.0 km) of the SR 76 widening project in May, while noting that there were several more steps in the legal process necessary before construction began.

[69] Two years later, concerns were expressed by environmental groups over the potential destruction of the habitat of the least Bell's vireo songbird by the construction of SR 76 and other projects in the region.

Fish and Wildlife Service approved the project, on condition that Caltrans purchase more land to set up habitat for environmental mitigation.

[73] Funds for the new Bonsall bridge were approved by the California Transportation Commission (CTC) in October 1988, and construction was scheduled to begin in early 1989.

[74] In November 1989, the California Coastal Commission gave the go-ahead for the realignment of SR 76 in western Oceanside, from I-5 to Frontier Drive.

[75] However, in February 1990, the Sierra Club, National Audubon Society, and League for Coastal Protection filed a lawsuit to have the approval overturned, citing concerns over the destruction of habitat.

[78] The following year, the city council voted to use the Lawrence Canyon land for commercial use instead of for the environmental mitigation, thus stalling the project.

[87] On June 12, 1996, the groundbreaking ceremony for the second phase of the project took place, by which time the completion date for the entire roadway had slipped to 2010.

[5][89] By 2002, Caltrans had two proposals for the part of the widening project between East Vista Way and Mission Road: building the new highway on top of the old one, or constructing a new roadway to the south of the San Luis Rey River.

[98] The Pala Indian band was required to pay for the costs to improve the road to mitigate the increased traffic levels from their proposed expansion.

[99] Construction began on widening the highway in April 2008,[100] and in March 2009, two lanes of a realigned 1.3-mile-long (2.1 km) segment of SR 76 opened east of I-15.

This improvement was intended to reduce accidents on a stretch of road that carried over 12,000 motorists per day, many headed for either the Pala Indian casino or a new gravel quarry that had recently opened.

[102] Construction started on widening SR 76 between Melrose Drive and South Mission Road in January 2010 to four lanes, funded by the federal and state governments and by TransNet revenue.

[104] Discussion on whether the route of the highway should go south or north of the river east of Mission Road began later that year, with residents expressing concerns about being able to make left turns.

[107] The westbound lanes between Melrose Drive and Mission Road opened to traffic in October,[108] with the entire roadway projected to be complete by the end of the year.

[109] A request by the city of Oceanside to restore access to Jefferies Ranch Road from SR 76 was declined by Caltrans in late 2012, due to concerns about future expressway expansion to six lanes.