360° panorama by Jason Perrone.
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Launched in 1915 in Mobile, Alabama, as a connector route between New Orleans and Florida, the Old Spanish Trail soon expanded to a transcontinental trail, linking St. Augustine, Florida, to San Diego, California. Begun with a bang, progress on the highway stalled in the late teens due to the war and the considerable expense of building bridges across the numerous waterways emptying into the Gulf of Mexico. After several years of near inactivity, the highway project shifted west to Texas and took on new vigor. Under the direction of Harral Ayres, Managing Director, the Old Spanish Trail Association successfully brought the highway to completion in 1929. The lure of the Old Spanish Trail auto highway continued to captivate travelers until the early 1960s when new interstates redirected traffic off the old road. This round coquina trail zero milestone marker in St. Augustine was dedicated during three days of pageants beginning April 2, 1929. The marker originally sat adjacent to then-Fort Marion Circle, south of the Castillo de San Marcos. In May 1962, the shell stone sphere was moved to the north side of the Visitor Information Center. Now it sits on the south side of that building.

http://www.360cities.net/image/old-spanish-trail-zero-marker