Who came up with the idea of the compromise

Well according to m knowledge the answer would be Henry Clay :) I hoped that this helped with your question :)

The Missouri Compromise was an effort by Congress to defuse the sectional and political rivalries triggered by the request of Missouri late in 1819 for admission as a state in which slavery would be permitted. At the time, the United States contained twenty-two states, evenly divided between slave and free. Admission of Missouri as a slave state would upset that balance; it would also set a precedent for congressional acquiescence in the expansion of slavery. Earlier in 1819, when Missouri was being organized as a territory, Representative James Tallmadge of New York had proposed an amendment that would ultimately have ended slavery there; this effort was defeated, as was a similar effort by Representative John Taylor of New York regarding Arkansas Territory. (Used from google. Small part of an article)