US Congressman. He was born in Central Top (or Central Township), Pennsylvania, to David McJunkin and Elizabeth Moore McJunkin and was educated at local common and public schools before entering the distinguished Jefferson College (later Washington & Jefferson College) in Canonsburg, Pennsylvania, where he graduated from in 1841. He then studied law and was admitted to the bar in 1843. On July 29, 1847, he married Jane Bredin in Butler, Pennsylvania, and the couple would have four children (Nancy Nannie was born in 1849, John Bredin was born in 1850, James Bredin in 1851, and Elizabeth Moore Libbie was born in 1853). He commenced to practicing in Butler, Pennsylvania, and later served as the Deputy Attorney General for Butler County, Pennsylvania, in 1850. His wife Jane passed away in December 1854 at the of 24 and he was left to raise their children alone. He also served as a Delegate to the Republican National Convention in 1860. During the Civil War (September 12-16, 1862, and September 26 to 28, 1862) he served as a First Lieutenant in Company G, 14th Pennsylvania Infantry Regiment. Following his military service, he resumed his public service duties. He then decided to run for a seat in the United States Congress and was elected. A Republican, he then served Pennsylvania's 23rd District (Forty-Second and Forty-Third Congresses) in the United States House of Representatives, serving from 1871 to 1875. While in the United States Congress he served as the Chairman of the United States House Committee on Expenditures in the Department of the Navy representing the Forty-Third Congress. He resigned from office on January 1, 1875. After his resignation from the United States Congress, he was succeeded in office by United States Representative John McCandless Thompson. He then served as a President Judge of the Seventeenth Judicial District of Pennsylvania from 1875 to 1885. He resumed his practice of law until he had to retire following a debilitating stroke in 1900. He passed away seven years later in Butler, Pennsylvania, at the age of 88, and was buried beside his wife Jane in the North Side Cemetery. At the time of his death, he had been in the law profession for more than fifty years and the oldest practicing law figure in Butler County, Pennsylvania.