Los Angeles County Transportation Commission acquired the
Southern Pacific Railroad Burbank Branch in 1992. When the line opened on October 26, 1992, service extended only as far as Pomona. It was incrementally extended to Claremont that December, Montclair the following February, then finally to San Bernardino in May 1993. Saturday service was added in 1997 and Sunday service in 1998 making it the first Metrolink line to offer weekend service.
San Bernardino Associated Governments (SANBAG) completed an
environmental impact report (EIR) in 2015 to extend Metrolink service southeast from the current eastern terminus in San Bernardino to
Redlands. The extension follows the
Redlands Subdivision and comprises two projects. The
Downtown San Bernardino Passenger Rail Project extended Metrolink southeast one mile via
double trackage to a new terminus at the
San Bernardino Transit Center. The project's
groundbreaking was in February 2014; at that time, the extension was expected to be completed by mid-2016. , the completion date had been extended to 2017. Construction work on the extension continued through March and April 2017. Test trains began running on the tracks in April 2017. This phase of the project opened to the public on December 16, 2017.
Arrow is a rail extension to Redlands. By December 2015, SANBAG decided that this second phase of the project, from the San Bernardino Transit Center to Redlands, would no longer be a Metrolink extension, but rather an independent system. SANBAG planned to use
diesel multiple units (DMUs) and have
Omnitrans operate the system. However, San Bernardino Line
express limited-stop trains would run on part of the extension, to a new station near the Downtown Redlands station.{{cite news|last1=Emerson|first1=Sandra|title=Where Redlands rail project is heading == Future development ==