Founded in 1913 by Edward Gardner Lewis and incorporated in 1979, the Atascadero Colony as it was known at the time was originally envisioned as a model community. Little evidence of Atascadero's original architecture and urban design remain, as historic buildings and homes have been torn down to make way for more modern developments and the Sunken Gardens bisected by Highway 101.
One of the few surviving examples of original urban design can be found, however, in the Rotunda Building located near the Junior High School on Palma Avenue in the Sunken Gardens public park. Designed by Walter D. Bliss of San Francisco, construction was completed in 1918 at a cost of $180,000. It served initially as the headquarters of the Atascadero Colony. This building was purchased by San Luis Obispo County in the 1950s as a Memorial Building. The building housed the county library, Atascadero Historial Social Museum and then the city offices following incorportation in 1979. The historic City Hall is adorned with a 40 foot dome atop the third story, originally intended to house the library. The building was designated a California Historical Landmark. The City Hall was damaged by the magnitude 6.5 San Simeon Earthquake on the morning of December 22, 2003. The building is currently undergoing restoration.
Another fine example of Atascadero's early architecture is The Carlton Hotel, built in 1929, located just west of the Sunken Gardens on El Camino Real, the city's main commercial street. Vacant since 1987, David Weyrich, a local millionaire, helped rejuvenate the derelict building with an approximately 12 million dollar renovation project completed in 2002.