The two ends of SR 16 were added to the state highway system by the third bond issue, passed by the state's voters in 1919: Route 50 from Lower Lake east to Rumsey and Route 54 from the Sacramento-Amador County line east to Drytown. Each was connected to Sacramento by existing or planned paved county highways. Although the exact alignment of Route 50 was not specified, the state Department of Engineering had already surveyed a 35-mile (56 km) route through Cache Creek Canyon pursuant to a 1915 law, which defined the Yolo and Lake Highway "following generally, the meanderings of Cache creek" but did not make it a state highway. By 1924, the California Highway Commission's engineers had realized that building Route 50 through the canyon was impractical, and adopted a substitute plan for two highways connecting Lower Lake and Rumsey with the planned Route 15 (Tahoe-Ukiah Highway, now State Route 20) to the north in September 1925. The western connection, to Lower Lake, became part of Route 49 (now State Route 53 there), which continued south from Lower Lake to Calistoga.