School in 1967, then moved to Duarte in 1990 as the Anita Oaks School.[23][24] The school owner's efforts to develop the property into a village of homes with the old mansion as its centerpiece were rejected by the city.[22] After an extended debate, with local citizens and regional preservationists efforts to preserve the historic main house, the city council voted to approve demolition for a real estate development by new owners in 1999.[22] The "Anoakia" mansion, all other significant estate structures and outbuildings, garden features, and numerous California sycamore and Coast live oak trees were demolished for 31 luxury home sites in 2000.[21] Some of the mansion's architectural elements were salvaged and removed. Only the gatehouse, on the estate's former southeast corner at Foothill and Baldwin, and theperimeter walls remain after the "Anoakia Estates" development was built.[21]

During World War I, Arcadia was home to the U.S. Army's Ross Field Balloon School, at the present-day Santa Anita Park site. Army observers were trained here in techniques to observe enemy activity from hot air balloons.

After World War I, Arcadia's population grew and local businesses included many chicken ranches and other agricultural activities. During the 1920s and 1930s, Arcadia began its transition to the residential city that it is today, as small farms and chicken ranches gave way to homes and numerous civic improvements, including a city library and a city hall. Scenes of many of Arcadia's interesting older sites can be viewed in a series of historic watercolors painted by local artists Edna Lenz and Justine Wishek.[25]