He served one term in the Wisconsin State Assembly, representing the city of Racine as a member of the Free Soil Party during the 1850 session.
[4] In April 1843, he was appointed by the Governor and Council of Massachusetts as a "Commissioner to Administer Oaths, &c." for use back in the Commonwealth; he was already a resident of Racine.
[5] Chapman was a delegate from Racine at the Chicago River and Harbor Convention of 1847.
[6] The convention drew 2,315 delegates from 19 states to advocate for federal support of improvements to inland rivers and harbors.
[7] In November 1847 he was among the officers of the first Masonic Lodge to be organized in Racine County.