Interstate 710 and State Route 710 (California)

Route 710, consisting of the non-contiguous segments of State Route 710 (SR 710) and Interstate 710 (I-710), is a major north–south state highway and auxiliary Interstate Highway in the Los Angeles metropolitan area of the U.S. state of California. Also called the Los Angeles River Freeway prior to November 18, 1954, the highway was initially planned to connect Long Beach and Pasadena, but a gap in the route exists from Alhambra to Pasadena through South Pasadena due to community opposition to its construction.

The completed southern segment is signed as I-710 and is officially known as the Long Beach Freeway, and it runs north from Long Beach to Valley Boulevard, just north of I-10 (San Bernardino Freeway), near the boundary between the cities of Alhambra and Los Angeles. South of Atlantic Boulevard at the Bell–Vernon border, I-710 follows the course of the Los Angeles River, rarely wandering more than a few hundred feet from the riverbed. South of SR 1 in Long Beach, I-710 is officially part of the Seaside Freeway.

SR 710 is the designation of the completed portion of the proposed northern extension of the route to Pasadena. This segment runs from California Boulevard in Pasadena north to its northern terminus at SR 134 and I-210. It remains unsigned, except for onramps onto the stub which are signed as onramps onto I-210 instead of SR 710. Legislation passed in 2019 authorizes its relinquishment to the City of Pasadena on or after January 1, 2024.

Prior to 1983, the road was not an Interstate, although it was built to Interstate Highway standards. Until 1964 it was State Route 15, but it was renumbered to State Route 7 in the 1964 renumbering because of the existence of I-15, and to I-710 in 1983. However, the northern stub still contains postmile markers designating such stub as both Route 7 and Route 710.