How has the number of slave and free states changed from 1820 to 1850?

Between 1820 and 1850, the number of slave and free states in the United States changed significantly due to westward expansion and the contentious issue of slavery. The Missouri Compromise of 1820 established a balance by admitting Missouri as a slave state and Maine as a free state, maintaining an equal number of states. However, as new territories were acquired, tensions rose over whether they would permit slavery, leading to the Compromise of 1850, which introduced California as a free state while allowing popular sovereignty for other territories. By 1850, the balance was increasingly strained, contributing to rising sectional conflict.