Explain how California's rapid population growth led to statehood in 1850 as part of the Compromise of 1850, including why California entered as a free state.
California's population had grown so fast because of the Gold Rush that it skipped the usual "territory" stage most future states went through, and applied directly for statehood. Delegates wrote a state constitution at a convention in Monterey in 1849, and that constitution banned slavery in California. On September 9, 1850, California was admitted as the 31st state of the United States.
California joining as a free state created a problem in Congress, which had been carefully balanced between free states and slave states. To keep peace, Congress passed a bundle of laws known as the Compromise of 1850: California entered as a free state, but the compromise also included a much stronger Fugitive Slave Act, and let the newer territories of Utah and New Mexico decide the slavery question for themselves later through popular sovereignty. Statehood, in other words, was not just a California story -- it was tangled up in the biggest, most difficult debate facing the whole country at the time.
Mastery looks like: They can state the date of California statehood, that it entered as a free state, and explain its connection to the Compromise of 1850.
Common stumbles: Thinking statehood was automatic once enough people arrived; missing the national slavery debate tangled up in California's admission.