Add primary road (before median-divided highway), and modern highway (freeway)
Add source for bridge geometry
Tag primary road (maybe should be trunk?) across Golden Gate Bridge
Connect and tag source on existing railroad tracks
Connect and tag source on existing railroad tracks
Extend railroad tracks from 1943 map
Tag existing railroad track with source
Add railroad tracks from 1941 map
Add railroad tracks from 1899 map
Extend railroad tracks from 1941 map
Add railroad tracks from 1941 map
Update start date based on USGS maps