“The Great Compromiser,” as Clay was called by this time, had one more mediating trick up his sleeve. In 1850, California, suddenly full of gold-seekers, applied for admission to the Union as a free state. Southerners dug in their heels, complaining that a free California would tip the balance in the Senate against their section. Clay offered them something they had long desired: a sterner fugitive slave law, one that would criminalize the common Northern practice of assisting slaves fleeing bondage.
Source: latimes.com – Los Angeles Times