Here we go again. Another county — this time San Bernardino — is threatening to break away from California to form its own state. Petitions and plots of this sort pop up almost annually but then invariably fizzle. Yet however quixotic state division may seem, it has a much deeper, grimmer history than most Californians recognize.

A real estate developer and two mayors in the Inland Empire are the latest would-be secessionists. San Bernardino County, they argue, should be a state unto itself. With 2.2 million residents, it would be more populous than 15 other states. They’ve dubbed the unborn state “Empire.” (Take that, New York, long the Empire State.)

Aspiring separatists have made more than 220 distinct attempts to reconfigure California. Most recent wannabe separatists, like those in San Bernardino, feed off frustration with California’s liberal governance. The proposed state of “Jefferson,” formed from California’s northernmost counties, is perhaps the best-known conservative attempt at a remapping of the West Coast.

But California’s state division movement goes much deeper than the right-wing critique of the current government. Separatism is as old as the state itself. And it’s bound up in California’s history of slavery.

Los Angeles is the original home of secessionism in the state. Nearly every year in the 1850s, aggrieved Angelenos lobbied to break away from California to form a separate territory. They complained of a regional imbalance in legislative representation and a tax system that placed disproportionate levies on Southern California landowners.

But for many separatists, the primary motive was to transform Southern California into the nation’s next slave state. Their logic: Once free from California, the breakaway territory could jettison the state’s Constitution, legalize human bondage — and become a haven for westering slaveholders.

Abraham Lincoln, then an obscure former Illinois congressman, warned of this possibility. In a list of resolutions he drafted in January 1855, Lincoln urged members of Congress “to resist, to their utmost, the now threatened attempt to divide California, in order to erect one portion thereof into a slave-state.”

Lincoln’s anxieties weren’t misplaced. True, Southern California was hundreds of miles from the nearest slave state. But Los Angeles was a good deal more “Southern” than its geographic location might suggest. Migrants from the slave states constituted a majority of the town’s U.S.-born population, and their political loyalties came west with them. The population of Los Angeles, one resident wrote in 1853, resembled “such as you find on the frontiers of Missouri.”