He graduated from Miami University in 1835 and at the Cincinnati Law School in 1837 being admitted to the bar the same year, practicing law out of his in office in Cincinnati.
Cary became well-known nationally as a prohibitionist author and lecturer. He was elected a judge in the Ohio State Supreme Court, but decided to pass the job up. Instead, he got the post of Paymaster General for the state of Ohio during the terms of Governors Mordecai Bartley and William Bebb.
He stopped working in law in 1845 to become a farmer and also to devote himself to temperance and anti-slavery groups.
He gave lectures and wrote books on prohibition and slavery matters. Cary then became Collector of Internal Revenue for Ohio"s first district in 1865.
In 1867, Cary was elected to the Fortieth Congress as an Independent Republican to represent Ohio"s second district, taking seat November 21, 1867. This was caused by the resignation of future United States President Rutherford B. Hayes who had just been elected Governor of Ohio.
There, he became the chairman of the Committee on Education and Labor.
Cary had also been the only Republican to vote against the impeachment of President Andrew Johnson. He lost the election to the Forty-first Congress in 1868 to Job East. Stevenson. In 1875, Cary ran for Lieutenant Governor of Ohio.
However, Cary lost his race to Thomas L. Young who would succeed to the governorship after Hayes resigned to become President of the United States.
Cary joined the Greenback Party and was the nominee for Vice President of the United States in the 1876 election after Newton Booth declined to run. He ran with Peter Cooper who was running for the presidency against Rutherford B. Hayes.
Cooper and Cary also came behind the Democratic Party candidates Samuel J. Tilden and Thomas A. Hendricks. Cary lived out the rest of his days writing literature and supporting fellow prohibitionists.
He was twice married, first to Maria Louisa Allen, October 18, 1836, she died of consumption, September 25, 1847.
They had three children: Martha Louisa (b 1837), Ella Woodnutt (b 1841) and Lou Allen (b 1847). They had three children: Olive (b 1851), Samuel Fenton, Junior. (b 1857) and Jessie (b 1858).
He died at the Cary Homestead in College Hill, Cincinnati, Ohio on September 29, 1900.
He is interred with his family in Spring Grove Cemetery in Cincinnati. Cary, North Carolina was named in his honor.