From the plaque:
Gold rush town and western
terminus of the Placerville-Carson Road to the Comstock,
Placerville was a relay station of the Central Overland
Pony Express from April 4, 1860 until June 30, 1861. Here
on April 4, 1860, the first eastbound pony rider, William
(Sam) Hamilton, changed horses, added an express letter
to his mochila, and sped away for Sportsman's Hall. Placerville
was the western terminus of the Pony Express from July
1, 1861 until its discontinuance on October 26, 1861.
Plaque placed by the California State Park Commission in cooperation with the El Dorado County Chamber of Commerce, James W. Marshall Chapter 49, E Clampus Vitus and Central Overland Pony Express Trail Association. April 2, 1960.