Erdman was elected as a Democrat to the Fifty-third and Fifty-fourth Congresses. He was not a candidate for reelection in 1896. He resumed the practice of law in Allentown. He served as a trustee of Muhlenberg College at Allentown. He was president of the Coplay Cement Manufacturing Co., the Allentown & Coopersburg Turnpike Co., and the Allen Fire Insurance Co. for many years. He died in Allentown in 1911 and was interred in Fairview Cemetery.[citation needed]