Born into slavery in Virginia in 1789, Meachum had earned enough money by age 21 to purchase his own freedom and that of his father. According to the short autobiography he published in 1846, he came to St. Louis in 1815 looking for his wife, who had been brought to Missouri by her owner. By his own account, Meachum arrived in Missouri with only three dollars in his pocket, but soon put his skills as a carpenter and cooper (barrel maker) to use and earned enough to purchase the freedom of his wife and children, as well as a residence for his family.

By 1826 he had been ordained a Baptist minister and became pastor of St. Louis´ First African Baptist Church (still in existence at a new location at 3100 Bell).

As a preacher and one of the city´s most prominent African Americans, Meachum was intensely interested in education and enhancing the welfare of his community. According to a newspaper published in Boston in 1836, he purchased 20 slaves in order to teach them skills. Once they had paid back most of their purchase price, he freed them. According to the same source (whose origin was probably the Rev. Meachum himself), "in 1835 he built a steamboat, which he has provided with a library, and made it a temperance boat."

In 1846, Meachum published a pamphlet in Philadelphia in 1846 calling for free persons of color across the U.S. to gather together to establish schools and programs of vocational education for their children. The pamphlet demonstrates his belief that people of color were citizens endowed with the same inalienable rights as any other, a position the Supreme Court would soon dispute in the case of two other adopted St. Louisans, Dred and Harriet Scott.

It does not appear that the convention he sought to convene in Pittsburgh the following year took place. Nevertheless, the fact that his call was issued in Philadelphia far from his St. Louis home and was signed by three African American leaders from Washington D.C., Rhode Island, and Pennsylvania indicates that Meachum saw himself as a leader on a national level. His stature was recognized locally by his election as first vice president of the Western Colored Baptist Convention, organized in Alton in 1853. It was also recognized by the Missouri Republican, St. Louis´ principal newspaper at the time, which printed a notice in 1854 that Meachum had died in his pulpit.