He studied law and was later admitted to the bar.
A native of Mercersburg, Franklin County, Pennsylvania, he moved with his wife to the Northwest Territory in 1793 and settled in Losantiville, which would later become Cincinnati, Ohio.
James Findlay practiced as an attorney until he was elected to the Legislative Council of the Northwest Territory in 1798. He became the United States Marshal of Ohio in 1802 and was elected to the First Ohio Legislature when Ohio became a state in 1803. He was elected President of the Cincinnati City Council, also referred to as Mayor, from 1805 to 1806 and again from 1810 to 1811. During the War of 1812, he was commissioned as Colonel of the 2nd Ohio Volunteer Infantry and commanded the regiment near Detroit. He erected a fort in southern Ohio and was also briefly held as a prisoner of war by the British. After the war, he became Major General of the Ohio Militia's First Division.
Findlay was an enormously successful real estate and business entrepreneur and also helped found Cincinnati's first library.
He died in Cincinnati in 1835 when he was 65 years old. He was originally buried in the Presbyterian Grounds and was later removed to Spring Grove Cemetery in 1854. Findlay, Ohio, is named for him as well as Findlay Market, and Findlay Street in Cincinnati. His brother, William Findlay was a Pennsylvania Governor and Senator, and another brother, John Findlay, was a Pennsylvania Congressman.
Elected as a Jacksonian Party member to represent Ohio's 1st District in the United States House of Representatives, he served from 1825 to 1833. He was not a candidate for reelection in 1832 and was an unsuccessful candidate as a Democratic Party member for Governor of Ohio in 1834.
He was married to Jane Irwin Findlay. Six years after his death, she lived in the White House with her niece, Jane Irwin Harrison, who had married President William Henry Harrison's son.