The Administration Building is designed with a Greek cross plan. In the middle of the cross are two rotundas, one above the other and are 100 feet in height. The domes of the rotunda have a coffered design. The dome of the building is tile. There are three floors of offices around the lower rotunda. The building has a total floor area of 48,942 square feet. The building is constructed from reinforced concrete and faced with terracotta brick. According to W.D Bliss, the overall design of the building is in the design of the Italian Renaissance.
The Administration Building was used as the chamber of commerce during the colony period. Other uses during this time included a bank, headquarters of of the water company, post office, real estate office, and other civic functions. After E.G Lewis was forced into bankruptcy, the new trustees sold the building. The building is currently being used as the Atascadero city hall and access to the public is allowed. The city hall gives guided tours of the historic building a few times a month.
In 1928 - 1933 Frank Moran purchased the Administration Building for use as the California Campus for Moran Prep and Junior College. He also bought the Printery and hospital to use for his school. The Administration Building was used for the Junior College while the prep school was housed in the printery. The Miramonte School and Junior college occupied the building following the Moran school. The school was incorporated in 1935 but failed and was repossessed in the early 1940’s.
Colonel Benjamin Aldrich bought the building and used it for the Acheson Polytechnic College. After his death, San Luis Obispo county bought the building in 1951 and used if for the veterans memorial building. In 1980, SLO county gave the building back to the newly formed City of Atascadero to be used for its city hall building. In 2003, the San Simeon earthquake forced the building to close. It was completely renovated and is now operating as the city hall building once again.
Edward Gardner Lewis purchased 23,000 acres of rolling hills from J.H. Henry in the Spring of 1913. The Atascadero Colony was created by Lewis who formed the Colony Holding Corporation to take care of promoting the Atascadero enterprise. It was referred to as a “dream city”. His motto was, “all the advantages of country life with city conveniences”. The Atascadero Administration Building was completed in 1918 at the cost of approximately $200,000.