US Congressman, Entrepreneur. He was a United States Representative from the State of Louisiana. He was born as Matthew Diamond Lagan in Maghera, County Londonderry, Ireland, on June 20, 1829. He was educated locally and attended the local common public schools and immigrated to the United States and settled in New Orleans, Louisiana, when he was fourteen years old in 1843. He then engaged in manufacturing pursuits and mercantile pursuits. Following the outbreak of the American Civil War, he fitted many vessels for the use of the Confederate States and later decided to serve his adopted country of the United States as a Volunteer in the Confederate Navy. He then entered politics and was elected to serve a term on the newly created New Orleans Common City Council in 1867. He also served as a Delegate to the Louisiana State Constitutional Convention in 1879, was again elected to another term on the New Orleans Common City Council in 1882, and served as both President and Acting Mayor during his term. He then decided to run for a seat in the United States Congress and was elected to succeed the outgoing United States Representative Nathaniel Dick Wallace (1845-1894), on March 4, 1887. A Member of the Democratic Party, he then served Louisiana's 2nd District (Fiftieth Congress), in the United States House of Representatives from March 4, 1887, to March 3, 1889. He declined a renomination for election to represent the Fifty-First Congress in the United States House of Representatives. Following his term in the United States Congress, he was succeeded by the incoming United States Representative Hamilton Dudley Coleman (1845-1926), on March 4, 1889. He then decided to run for a second term in the United States Congress in 1890 and was elected to succeed his successor United States Representative Hamilton Dudley Coleman (1845-1926), on March 3, 1891. A Member of the Democratic Party, he then served Louisiana's 2nd District (Fifty-Second Congress), in the United States House of Representatives from March 4, 1891, to March 3, 1893. Following his second term in the United States Congress, he was succeeded in office by the incoming United States Representative Robert Charles Davey (1853-1908), on March 4, 1893. After leaving the United States Congress, he retired from politics and returned to public life in New Orleans, Louisiana. He passed away following a long illness of four years at the family home at No. 1209 Annunciation Street in New Orleans, Louisiana, on April 8, 1901, at the age of 71. Following his death, his funeral service was held at the family home at No. 1209 Annunciation Street in New Orleans, Louisiana, with a remembrance in his honor which was officiated by the Reverend P.M. Massardier at St. Theresa's Church in New Orleans, Louisiana, which concluded with his being buried in the Family Tomb in Metairie Cemetery in New Orleans, Louisiana. He was married to Jane Claiborne Laycock Lagan (1837-1906), a prominent charity worker, with whom he had five children including, Matthew Diamond Lagan Jr. (1863-1917), Sara Lagan DeBuys (1871-1922), and Charles H. Lagan (1857-1920). His wife Jane passed away in New Orleans, Louisiana, on August 21, 1906, at the age of 69, and she was buried with him in the Family Tomb at Metairie Cemetery in New Orleans, Louisiana. The funeral service was considered one of the most largely attended burials seen in the city of New Orleans, Louisiana, with over one hundred prominent people in attendance at that time.