His studies were interrupted by World War I, during which time he served with the United States Navy Aviation Corps.
In 1940, he was appointed by the New Jersey Legislature as director of the Municipal Aid Administration, and he became Commissioner of Economic Development in 1944.
In 1949 he was appointed Commissioner of the newly created New Jersey Department of Conservation and Economic Development, serving until 1954.
During his term of office he acquired large tracts for use as public lands, including Wharton State Forest in the Pine Barrens and stretches of beaches on the Jersey Shore.
[2] In 1958, Erdman was elected as Chairman of the New Jersey Republican State Committee, succeeding the late Samuel L. Bodine.