Gorman was born in Woodstock, Maryland and attended the local public schools. He was appointed as a page in the House of Representatives in 1852 and was transferred to the Senate through the influence of Illinois senator Stephen A. Douglas, who made him his private secretary. Gorman subsequently served the Senate as page, messenger, assistant doorkeeper, assistant postmaster, and finally postmaster.

In September of 1866, Gorman was removed from his Senate office and was immediately appointed collector of internal revenue for the fifth district of Maryland. He later served as director and eventually president of the Chesapeake Ohio Canal Co.

Gorman was elected to the Maryland House of Delegates in 1869, serving until 1875; he served as speaker of the house for one session. In 1875, he was elected to the Maryland State Senate, serving until 1881.

In 1880, Gorman was elected to the United States Senate. He served as the Democratic caucus chairman from 1890-1898, as the chairman of the Senate Committee on Printing (Fifty-third Congress), and as a member of the Senate Committee on Private Land Claims (Fifty-fifth Congress). Gorman was reelected in 1886 and 1892, but was an unsuccessful candidate for re-election in 1898, losing to Louis E. McComas.

After his defeat, Gorman campaigned for the other Maryland senate seat, and was successfully elected to the U.S. Senate in 1902. He was again appointed as the Democratic caucus chairman from 1903-1906, and served as senator until his death in Washington, D.C. in 1906.

This article incorporates facts obtained from the public domain Biographical Directory of the United States Congress.