In 1873, he was hired by architect John McArthur Jr., to produce models for the sculptures adorning Philadelphia City Hall. The commission required more than 250 marble and bronze pieces and took Calder twenty years to complete. That same year, Calder was commissioned by the forerunner of Philadelphia's current Association for Public Art, the Fairmount Park Art Association, to create an equestrian statue of Major General George Gordon Meade for Fairmount Park. Then in 1875, he won the competition for the colossal (37 foot tall) bronze statue of William Penn that was to crown the new City Hall's tower. That portrait sculpture remains to this day the largest atop any building in the world.[3][4][5]
Bach, Penny Balkin, Public Art in Philadelphia, Temple University Press, Philadelphia, Pennsylvania, 1992 ISBN0-87722-822-1
Craven, Wayne, Sculpture in America, Thomas Y Crowell Co, NY, NY 1968 ISBN0-87413-225-8
Fairmount Park Association, Sculpture of a City: Philadelphia's Treasures in Bronze and Stone, Walker Publishing Co., Inc, NY. NY 1974 ISBN0-8027-7100-9
Hayes, Margaret Calder Three Alexander Calders, Paul S Eriksson Publisher, Middlebury, Vermont, 1977 ISBN0-8397-8017-6
Kvaran and Lockley, A Guide to Architectural Sculpture in America, unpublished manuscript
Williams, Oliver P., County Courthouses of Pennsylvania: A Guide, Stackpole Books, Mechanicsburg, PA 2001 ISBN0-8117-2738-6