As a student, in 1841, he studied law in the office of Forsyth & Lindermau in Kingston, New New York
His early education was in a private school in Litchfield County, Connecticut and the Kingston Academy in Ulster County, New New York In 1844, he was admitted to the bar of the New York Supreme Court. Foreign four years, Catlin practiced law in New New York
On January 8, 1849, Catlin traveled by ship from New York City to San Francisco.
While living there, Catlin mined and practiced law. In 1850, he moved to Sacramento and began to practice law there.
While living in Sacramento, Catlin witnessed the Squatters" Riot. Catlin offered the name "Natoma", meaning clear water in the local native dialect.
Catlin had already established the Natoma Mining Company to do his mining work.
Once the post office was established in that area of Sacramento County, it became the Natoma Township. In 1860, Catlin married Ruth Anne Coningham Donaldson. In 1852, after a failed attempt at getting an Assembly seat, Catlin was elected to the State Senate.
During his tenure as State Senator, he authored the law that made Sacramento the permanent seat of government in the State of California.
In 1857, he was elected to the State Assembly for Sacramento County. He served in that capacity until 1876, when the Supreme Court of California declared most of the powers granted to the Board were unconstitutional and it was abolished.
In 1875, Catlin was proposed as a candidate for Governor of California, but lost the nomination to John Bidwell. In 1890, Catlin was elected as a judge in the Superior Court of Sacramento County.
He served until 1897 and then went back to his private practice.
Catlin died November 5, 1900 in Sacramento, California.
During his political career, Catlin was a member of the Whig Party, the Know Nothing Party and the Republican Party.
In 1872, Catlin was appointed to be one of three members of the State Board of Equalization.