Brewster was a lawyer from South Carolina, born there in 1816. He came to Texas in April 1836 to join the Texas Army and was assigned to serve as the private secretary for Sam Houston. He served brief stints as acting Secretary of War and Secretary of Navy before moving to Brazoria to establish a law practice. During his legal career he also served stints as the Brazoria County District Attorney and as state Attorney General, appointed by Governor George Wood. He move to Washington, D. C., in 1855 to open a law office and resided there until the start of the Civil War. He returned to Texas to join the Confederate Army. After the war he continued practicing law in San Antonio until his death in 1884. Brewster County was named in his honor.