What made California's admission as state controversial?

California's admission as a state in 1850 was controversial primarily due to the debate over slavery. The discovery of gold in 1848 led to a significant influx of settlers, and California's rapid population growth prompted it to apply for statehood as a free state. This upset the balance between free and slave states in the Senate, leading to tensions that contributed to the broader sectional conflict in the United States. The situation was partly resolved through the Compromise of 1850, which allowed California to enter as a free state while introducing other contentious measures regarding slavery in the territories.