[7][8] Many credited the former Mayor of San Jose, Ron Gonzales, with bringing this project to fruition.

[6] Santa Clara County was originally planned to be part of the BART system, but local governments did not approve.

In 2000, Santa Clara County voters approved a 30-year half-cent sales tax increase to fund BART,[14] which took effect in April 2006.

[21] By a two-thirds majority, Santa Clara County voters approved Measure B in November 2008, implementing a 30-year, 1/8-cent local sales tax dedicated solely to funding the operating and maintenance costs associated with the BART Silicon Valley extension.

[22] The economy worsened in 2009, and the 2000 sales tax was projected to generate $7 billion—short of the originally expected $11 billion.

[33] VTA also sought $1.5 billion from New Starts, and $750 million from the California Cap and Trade program.

[34][35][36] In 2018, VTA was awarded $2.6 billion for the project from the state's Transit and Intercity Rail Capital Program funded by the 2017 gas tax bill.

[38] $140 million was included in the version of the American Rescue Plan Act of 2021 passed by the House of Representatives, but was dropped in the Senate.

A proposed infill station at Calaveras Boulevard in downtown Milpitas has been deferred until the city secures funding.

Originally the entire Silicon Valley Extension from Fremont to Santa Clara was proposed as one megaproject, but lower than expected federal funding and sales tax revenue eliminated some stations from the original project and caused the division into two phases.

[14] A local industrial park sued in 2011, without success, on environmental grounds claiming that the extension would reduce vehicular access.

[14] The line would continue underground to the San Jose Diridon station, a transfer point to Amtrak, Caltrain, Altamont Corridor Express, VTA light rail and bus, and the planned California High-Speed Rail system.

The extension would then surface and continue to the site of the current Santa Clara Caltrain Station.

[3] A 40-acre (16 ha) BART maintenance yard would also be created at Newhall as part of this phase, using land just south of Santa Clara station that was purchased by VTA from Union Pacific.

However, BART preferred dual bores, as used elsewhere in its system, to cut construction cost and standardize the procedure for emergency evacuations.

[73] The design decision was postponed for three months;[77] in March, BART and VTA reached agreement on a single bore.