Rivington was a town in North Carolina. It was an obscure, overlooked hamlet until members of the Afrikaner Weerstandsbeweging set up their headquarters in Rivington after travelling back in time from the 21st century. Because of this they were known as "The Rivington Men" though they in fact had no connection to the townspeople, themselves quite ordinary southerners.
In 1864, Nate Caudell's train stopped in Rivington during his trip home to Nashville, North Carolina after being discharged from the army. Caudell disembarked to stretch his legs and looked around. He noticed a row of new warehouses guarded by men in the green-brown clothing of the AWB. Given that the lay-over was for only a half hour, Caudell along with Mollie Bean who was remaining in her home town, went to the First Rivington Bank to cash their pay warrants. Both were surprised to be paid in gold rather than bank notes but were pleased since it was worth significantly more. Before Caudell reboarded the train, he made Bean promise to write him and tell him about the changes in the town that they hadn't had a chance to explore.
Rivington was spared any direct fighting during the Confederacy's years-long war to gain independence from the United States. However, it became a battlefield when the AWB group turned from allies into bitter enemies of the Confederate government in 1868.
Lead by the legendary General Nathan Bedford Forrest, Confederate forces besieged the town with superior numbers. But the Rivington Men used modern mortars, sniper rifles, and machine guns to defend the town, effectively cancelling the Confederate advantage. A stalemate persisted until former US Colonel (and civilian mining engineer) Henry Pleasants, now a private in the Confederate Army, had an idea to dig under the enemy defenses and set off explosives under their lines.
The siege continued for two months until Pleasants' plan was ready. The explosion blasted the lines around Rivington apart, and Confederates rushed the town before another defensive line could be established. The Rivington Men began to fall back to their time machine and escape. However, Confederate Infantry destroyed the machine, forcing the remaining ninety militants to surrender.
Harry Turtledove confirms in The Guns of the South afterword that Rivington is completely fictional, though a fairly typical southern town of the time - aside from time travellers having established themselves there.