In 1852, Ireland moved to Texas, where he settled in Seguin and practiced law. Two years later, he married Mathilda Wicks Faircloth. She died in 1856, and the following year Ireland married Anna Maria Penn. Ireland was elected the mayor of Seguin in 1858. A firm believer in states' rights, Ireland was an ardent secessionist and served as a delegate to the 1861 Secession Convention. He volunteered as a private in the Confederate Army in 1862 and advanced to the rank of lieutenant colonel, 8th Texas Infantry (Hobby's Regiment). Throughout the Civil War, Ireland served within the Texas borders, patrolling along the Rio Grande border and along the Gulf Coast.

Following the war, Ireland participated in the Reconstruction Convention of 1866 and was soon elected judge of the Seguin District. He was removed from his position the following year when Radical Republicans seized power.

Ireland reentered politics in 1872, when he was elected to the Texas House of Representatives and chaired the executive committee of the Democratic party. In 1875, he served as an associate justice on the Texas Supreme Court. Later that year, and was a delegate to the Constitutional Convention. In late 1875, Ireland decided to run for the U.S. Senate. His primary competition was the current Governor of Texas, Richard Coke. Ireland lost the election and remained in the Texas House.

During his time as a state legislator, Ireland backed the bill creating the University of Texas at Austin. He was also a proponent of low taxes and favored regulating the railroads. In 1882, Governor Oran Roberts declined to run again, and Ireland received the Democratic nomination. He won the Governor's position by over 48,000 votes. One of his first acts as governor was to have an amendment added to the state constitution establishing an ad valorem tax. He also reformulated the policy for selling public lands. Construction began on the new Texas State Capitol building during Ireland's tenure. At his insistence, the building was constructed of Texas pink granite instead of imported Indiana limestone. After completing his second term in office, Ireland again ran for a US Senate seat and again lost. He returned to Seguin to practice law. His profits were invested in land and railroad stocks. During the panic of 1893, Ireland lost everything. He died on March 15, 1896 and is buried in the Texas State Cemetery in Austin