He served three terms in the New York State Assembly (1825–1826, 1829).
He moved with his father's family first to Madison County, and then to Hanover, New York in 1817.
In 1816, he had purchased Jonathan Bartoo's mill property.
He ran again in 1826, but lost to Elial Foote and Samuel Brown.
[3] Mixer again served in the 51st New York State Legislature alongside Nathaniel Fenton from January 1—December 31, 1828 and in the 52nd New York State Legislature alongside Abner Hazeltine from January 1—December 31, 1829.