The first light rail line of the RT, which opened in 1987, was an route between Watt/I-80 station in North Sacramento, through downtown, and continuing east on Folsom Boulevard to Butterfield Way station. It was built at a cost of $176million
USD ($ in adjusted for inflation), which included the cost of vehicles and maintenance and storage facilities. Much of the line, when it was first built, was single-tracked, though improvements over the 1990s allowed much of the original system to be double-tracked. The line was built mainly using the
Sacramento Valley Railroad right-of-way, and a extension to the Mather Field/Mills station was completed in 1998. In June 2004, a further extension from Mather Field/Mills to Sunrise was opened. On September26, 2003, the
South Line (now part of the
Blue Line) opened for between the 16th Street station on the Watt/I-80-Downtown-Mather Field/Mills line and a station at Meadowview Road in the south end, which is the first phase of a planned longer line to Elk Grove. Much of the extension follows a railroad right-of-way. When it opened, 7 new stops were added to the system. In June 2005, following a reconfiguration of the light rail system, the Sunrise–Downtown Line was created (trains formerly continued beyond the downtown St.Rose of Lima Park station to Watt/I-80); it runs from St.Rose/K-Street to Sunrise with an extension to the Folsom area that opened on October15, 2005. It has since been redesignated in color as the Gold Line. On December8, 2006 it was extended even further to the
downtown Amtrak depot (a.k.a. the Sacramento Valley Station), which provided interchanges between the light rail system and
the national rail system for the first time. Prior to 2025, headways were limited to 30 minutes between Sunrise and Historic Folsom stations due to single tracking on the east end between Parkshore Drive and Bidwell Street. Sac RT released a study in 2020 on the possibility of adding additional
passing sidings in the area to run twice as many trains in addition to reconfiguring station platforms for use with new
low-floor rolling stock. The project to add a passing loop near
Glenn station broke ground in 2023 and was completed in January 2025. While originally intended to run 15 minute headways at all Folsom area stations, , the line runs a modified schedule of three trips per hour between Sunrise and Historic Folsom stations with a mix of 15 and 30 minute headways, using new
Siemens S700 low-floor rolling stock on the line. By 2025, a new
infill station was planned at Horn Road. ==Line description==