 Chapman served as a member of the Maryland House of Delegates from 1824 to 1832 and from 1843 to 1844, serving as Speaker of the House from 1826 to 1829 and again in 1844.He served as a member of the Maryland State Senate from 1832 to 1836, and served as President of the Senate from 1833 to 1836.He also served in the State militia, and was an unsuccessful candidate for Governor of Maryland in 1844.