California's El Camino Real, ("The Kings Highway"), was created by Spanish explorers and Spanish Missionaries traveling from Mexico into the northern wilderness of California in the early 19th century. The Missionaries created the California
Spanish Missions.
The San Francisco Solano Mission, (as it is commonly called) was founded and built by Padre Jose Altamira in 1823. This was the last and most northerly of the twenty-one Franciscan missions, and the only one founded under Mexican rule. It also marked the northern terminus of El Camino Real -- the King's Highway -- the main road north from Mexico.
El Camino Real is still California's longest street. While hidden in many places by modern roads, it continues to serve as a major thoughfare in California.