Welty McCullogh was born in Greensburg, Pennsylvania. He attended the common schools and Washington and Jefferson College in Washington, Pennsylvania. He served as second clerk under Captain W. B. Coulter, provost marshal of twenty-first district of Pennsylvania, during the American Civil War. He graduated from Princeton College in June 1870. He studied law, was admitted to the bar in 1872 and commenced practice in Greensburg. He served as assistant solicitor for the Baltimore & Ohio Railroad.

McCullogh was elected as a Republican to the Fiftieth Congress. He was an unsuccessful candidate for renomination in 1888. He continued the practice of law until his death in Greensburg in 1889. Interment in the new St. Clair Cemetery.

• United States Congress. "Welty McCullogh (id: M000394)". Biographical Directory of the United States Congress. Retrieved on 2009-04-26
• The Political Graveyard