Colton is a city in San Bernardino County, California, United States. Colton is the site of Colton Crossing, one of the busiest at-grade railroad crossings in the United States. The main transcontinental trunk lines of Union Pacific and Burlington Northern Santa Fe cross at this point. As traffic on each line has soared since the mid-1990s, fueled largely by the vast increase in imports passing through the ports of Los Angeles and Long Beach, the primitive crossing has become a serious bottleneck. The crossing was installed in August 1882 by the California Southern Railroad to cross the Southern Pacific Railroad's tracks while building northward from San Diego.