Foothill Extension

The Foothill Extension (formerly the Gold Line Foothill Extension) is a construction project extending the light rail A Line, a part of the Los Angeles Metro Rail system. The project begins at the former terminus of the former Gold Line at Sierra Madre Villa station in Pasadena and continues east through the "Foothill Cities" of Los Angeles County. The plan's first stage, "Phase 2A", extended the then-Gold Line to APU/Citrus College station in Azusa; it opened on March 5, 2016. The first part of "Phase 2B" extended the now A Line a further four stations to Pomona North station on the Metrolink San Bernardino Line in Pomona, thereby returning passenger rail service to the full right of way originally built out by the Los Angeles and San Gabriel Valley Railroad in 1887. It broke ground in December 2017 and opened on September 19, 2025.

The second part of Phase 2B will further extend the line east to the Claremont San Bernardino Line station. Construction is expected to break ground in 2027 and be completed in 2031.

The corridor extension is being planned, managed, and implemented by the Foothill Gold Line Construction Authority, simply known as Foothill Gold Line. The joint powers authority is governed by appointees from Los Angeles Metro, the San Bernardino County Transportation Authority (SBCTA), the San Gabriel Valley Council of Governments (SVGCOG), and the cities of Los Angeles, South Pasadena, and Pasadena. In addition to enhancing mobility in one of the most congested metropolitan areas in the United States, the 23.8-mile project (38.3 km) is seen as an economic catalyst for the region, generating 6,900 jobs during the construction phase and creating infill and transit-oriented development opportunities.

With the Regional Connector having opened on June 16, 2023, the north (Pasadena–Azusa–Pomona) branch of the then-L/Gold Line was absorbed into the A Line, providing service from Long Beach via Downtown Los Angeles and Pasadena to Azusa.