[1] Koerner began his career in Pittsburgh, Pennsylvania, where he worked alongside architect Sidney F.
[1] Koerner moved to California, where he designed private residences and government buildings in Los Angeles County, especially in Beverly Hills.
With William J. Gage, they designed a seven-bedroom house in the Renaissance Revival style in Beverly Hills in the mid-1920s.
[2] The two men designed the Beverly Hills City Hall in the Spanish Colonial Revival style in 1931, and they attended its dedication in April 1932.
[3] Koerner also designed the Beverly Hills Fire Department building and the Pacific Electric Railway's Beverly Hills station.