From the Wikipedia article on State Route 275, now known as Tower Bridge Gateway:

In 1993, the West Sacramento City Council approved the “Triangle Specific Plan” for a new downtown in the triangle bounded by the Sacramento River, SR 275, and US 50; this plan included downgrading the freeway to a surface road. The state legislature passed a law in 1994 that allowed Caltrans to come to an agreement with West Sacramento or Sacramento for the relinquishment of any part of SR 275. Although no portions had yet been relinquished, the legislature deleted Route 275 from the Streets and Highways Code in 1996.

The Triangle redevelopment happened slowly, with the first part — Raley Field — opening in 2000. Effective January 1, 2001, Caltrans relinquished SR 275 to West Sacramento between postmiles 12.4 (west of Riske Lane) and 13.0 (the west end of the Tower Bridge). The city renamed the road Tower Bridge Gateway and demolished the Riske Lane overpass in early 2007, replacing it with a signalized intersection that now serves the new Garden Street. A planned removal of the 3rd Street underpass and addition of two more intersections at 5th and 3rd Streets is contingent on funding and relocation of a Union Pacific Railroad track.