The zero milestone of the Old Spanish Trail is a spherical monument made of coquina shells located south of the St. Augustine Visitor Center. The milestone marks the end of the Old Spanish Trail auto highway that was completed in 1929 and linked San Diego, California and St. Augustine, Florida. This trail was one of the country’s original interstate routes and the highway’s name pays homage to the Spanish heritage and missions of the southwest and the south.
The Old Spanish Trail (OST) was an early 20th-century highway project intended to provide a continuous road route from California to Florida, linking together the southwestern and southern states. The trail is one of the first interstate roads in the United States.
Planning and construction of the OST highway system began in 1915 and the highway was officially opened for travel more than a decade later in 1929. The OST highway follows what eventually became known as U.S. Highway 80 in the southwest and U.S. Highway 90 in the south.
The OST was originally developed as a touring route for automobiles through Florida, Alabama, Mississippi, Louisiana, Texas, New Mexico, Arizona, and California. The original route is now the location of several parts of current highways including US 80, US 90 and US 290. These roads were later replaced by the interstate system and a significant part of the Old Spanish Trail can now be travelled by taking I-8 and I-10.