In February 1820 the Senate passed a bill for the admission of Maine with an amendment enabling the people of Missouri to form a state constitution. Before the bill was returned to the House, a second amendment was adopted on the motion of Jesse B. Thomas of Illinois, excluding slavery from the Louisiana Territory north of the parallel 36°30′ north (the southern boundary of Missouri), except within the limits of the proposed state of Missouri. The House then approved the bill as amended by the Senate.[87]
The legislation passed, and became known as "the Missouri Compromise". Though Monroe remained firmly opposed to any compromise that restricted slavery anywhere, he reluctantly signed the Compromise into law (March 6, 1820) only because he believed it was the least bad alternative for southern slaveholders. The Missouri Compromise temporarily settled the issue of slavery in the territories.[88]

Internal improvements

Bureau of Engraving and Printing (BEP) engraved portrait of Monroe as President

As the United States continued to grow, many Americans advocated a system of internal improvements to help the country develop. 