 Trumbauer was born in Philadelphia, the son of Josiah Blyler Trumbauer, a salesman, and Mary Malvina (Fable) Trumbauer.He completed a 6-year apprenticeship with G. W. and W. D. Hewitt, and opened his own architectural office at age 21.He did some work for developers Wendell and Smith, designing homes for middle-class planned communities, including the Overbrook Farms and Wayne Estate developments.