According to my Glendale high school days, the road along the ocean that stretched from San Diego to San Francisco was staked out in the 1780's or so by the Spanish. The Spanish were afraid the French or Russians would claim the land along the coast first. France had picked up a big chunk of land between the Mississipi and the Rocky Mountains. Russia was coming south across the Berring Sea and down the coast from what would eventually be Alaska. The first big push to stake out the royal road stopped at what became Los Angeles. The whole point of the road was to set up a link between the Franciscan missions in California.