Peck also helped establish the Illinois State Baptist Convention in 1834, and became its first president. He wrote prolifically, including on agriculture, frontier history and Native American matters. In 1843 he founded the American Baptist Publication Society. Peck also established a weekly religious journal, the "Western Pioneer." Harvard University awarded Peck an honorary degree in 1852. Two years later, Illinois' legislature commissioned him to write the first history of the state. Peck also founded the Western Baptist Historical Society, and briefly served in Covington, Kentucky.