Representative from Allamakee county, was one of the nine children of Michael Smith O'Brien and Henrietta Alice O'Brien. He was born in Oneida county, New York. Came to Allamakee county, Iowa, with his parents in September, 1870. He drove ox teams and worked on farms until 1884, when he went to northwestern Iowa and South Dakota and herded cattle. In 1891 and 1892 he worked as a carpenter at Sanborn, Rock Rapids and Sioux Falls. He also worked as a carpenter and builder in Birmingham, Alabama, and Jackson, Mississippi. In 1892 and 1893 he helped install exhibits at the exposition in Chicago and in May, 1893, was appointed as one of the Columbian Guards at the World's Columbian Exposition, Chicago. At the close of the exposition went to California. Put up Canadian exhibits at the Midwinter Exposition in Golden Gate Park in the winter of 1893 and 1894. In 1894 he returned to Waukon, Iowa, following the trade of contractor and builder until 1898. He was a member of Company "I", 49th Iowa National Guard for several years. A few days after war with Spain was declared he went to Pensacola, Florida, and enlisted May 5th, 1898, in the regular U. S. Navy for one year as first class petty officer. He was honorably discharged at the close of the war with Spain. Returned to Waukon. Was admitted to the bar in 1899 and in connection with practice of law engaged extensively in real estate business and was interested in stock ranch and farms in North Dakota and Iowa. In 1902 he was married to Miss Decorah Grattan, at Medford, Oklahoma. They have two sons, Henry Grattan O'Brien and John Gordon O'Brien. He is a member of the Knights of Pythias, Bayard Lodge No. 121, Waukon, Iowa. In politics a republican. Elected to the forty-third general assembly in 1928.