As an architect, Muhlenberg apprenticed with Charles Barton Keen, Magaziner & Potter, and John T. Windrim in Philadelphia. In 1917 he began operating independently, and on May 1, 1919, following his service in World War I, he announced a reopening of his Philadelphia office. In 1920, Muhlenberg joined the Philadelphia Chapter of the American Institute of Architects, and opened an office of Frederick A. Muhlenberg, Architect, in Reading. He is listed in the Philadelphia city directories as an architect in 1921, 1922 and 1923, with his residential address given as Reading. By the mid-1920s, the practice, now located exclusively in Reading, was thriving. The firm continued through several reorganizations to its present form as Muhlenberg Greene Architects. During the intervening years, to accommodate the reorganizations, the firm operated for various periods under the following names :
Muhlenberg served on the Reading City Council from 1932–1936, and he was a councilman for the Borough of Wernersville during the 1920s, where he returned to live in his later years. He became the Republican Party chairman for Berks County from 1935–1940. In 1946, Muhlenberg was elected to the 80th Congress from Pennsylvania. He became the seventh member of his family to be elected to the U.S. Congress, where he served in the House of Representatives from January 3, 1947, until January 3, 1949; but he lost a re-election bid in 1948, defeated by Democrat George M. Rhodes.
Retirement
In a personal biography he furnished to the Reading Eagle, Muhlenberg listed the accomplishments of a "life built on service in four separate careers: architecture, military, social service and political." Retiring officially from Muhlenberg Greene Architects in 1977, one week after his 90th birthday, Muhlenberg continued to go to the office daily, until physical limitations prevented him from doing so about a year later. "You can't actually retire," he said at the time. "There really isn't any such thing. I don't intend to sit on my fanny and do nothing. At 90 years old, you change and have physical limitations. The pace may slow down, but the ideas are still there." Muhlenberg died at 92 years of age in Reading on January 19, 1980. As a veteran, he was buried in Arlington National Cemetery. A collection of awards, military medals, paperwork and other items related to Representative Muhlenberg is held by the Historical Society of Berks County.
Associations
Frederick Muhlenberg served as chairman for numerous civic and professional organizations, including the Association of Schuylkill River Municipalities, Director of the American Red Cross Berks County Chapter, Chairman of the Red Cross Disaster Relief Commission, the State Board of Examiners of Architects, President of the Social Welfare League, Public Charities Association, and the State Art Commission. Most notably, he served at the Berks County Planning Commission, leading as Chairman from the Commission's founding in 1954 until 1972 when he retired. In addition, he was a member of the Salvation Army Advisory Board. Muhlenberg served as commander of Gregg Post, American Legion, in 1924, and a member of General Hunter Liggett Post, No. 38, Veterans of Foreign Wars, and Reading Post, No. 10, Disabled American Veterans.
Awards
Listed in Who's Who in America, Muhlenberg received scores of educational, civilian, military and social service awards, including:
