The I-780 state-maintained freeway begins at Lemon Street and Curtola Parkway, quickly crossing underneath I-80 at a cloverleaf interchange.

The freeway passes through parts of unincorporated Solano County, then heads southeast along the Benicia State Recreation Area (a marsh).

[11][12] On September 15, 1955, the Bureau of Public Roads approved the Interstate Highway System spurs and connections in urban areas.

[13][14] The first piece of this freeway north of the Carquinez Strait was at the I-80 cloverleaf interchange, built in the late 1950s when I-80 was upgraded through Vallejo.

In 1975, a proposed (and never constructed) extension west and north to SR 37 east of the Napa River was added to LRN 141.

[24] LRN 141 was deleted from the state highway system in 1988,[25] soon after the city of Vallejo constructed Curtola Parkway over (replacing Maryland Street) just to the south, directly connecting I-780 with a surface road to SR 29.