Richard J. Oglesby was born on July 25, 1824 in Oldham County, Kentucky, the son of Jacob and Isabella Oglesby. His father was a farmer. In 1832, his parents, two brothers and a sister died of cholera and the family property was sold.
An uncle took the orphaned boy to Decatur, Illinois where he attended the district school a few months before he began to work for a livelihood as a farmer, rope maker, and carpenter. He was an ambitious lad and studied law in the office of Silas W. Robbins of Springfield, Illinois. He was admitted to the Bar in 1845, and practiced his profession at Sullivan, Illinois until the start of the Mexican War.
During the war, he served as first Lieutenant in the 4th Illinois Volunteers, and he participated in the battles of Vera Cruz and Cerro Gorda.
After the war, he resumed his law practice and attended a course of lectures at a law school in Louisville. In 1849, he rushed to California in search of gold, but returned to Decatur in 1851 and resumed his law profession. Five years later, he went aboard for 20 months traveling in Europe, Egypt, and the Holy Land.
Upon his return, he decided to enter politics. He had been a Whig and had served as a Scott Elector in 1852, but joined the Republican Party upon its formation. Six years later, he ran for Congress on the Republican ticket and was defeated by only a small majority.
In 1860, he was elected to the State Senate.
He resigned in 1861 on the occasion of the outbreak of the Civil War, and he became Colonel of the 8th Illinois Volunteers.
He served as brigade Commander under General Grant at Fort Henry and Fort Dearborn and was severely wounded at the Battle of Corinth. In April 1863, he returned to the Army and was promoted to the rank of Major General. He resigned from the army in May 1864.
He returned to Illinois and continued in politics. In November 1864, he was elected Governor of Illinois on the Republican ticket. He was an ardent advocate of Lincolns policies; however, later he bitterly denounced President Johnson's policies.
During his administration, Illinois ratified the thirteenth and fourteenth Amendments. He further enacted laws providing a home for the children of deceased soldiers and a school for the mentally ill.
At the end of his term, he returned to his law practice, but in 1872, he was again the Republican nominee for Governor. The party realized he was the only Republican who could carry the state. There was an understanding, however, that the Lieutenant Governor should succeed to the governorship immediately after Oglesby's inauguration and that Oglesby in turn should receive election to the U.S. Senate.
In 1884, the Republican Party nominated him Governor by acclamation. He became the first man in Illinois to receive that honor three times.