In the 1840s, John C. Fremont led three or four expeditions to the American West, gained a reputation as something of a romantic adventurer, and was dubbed "the Pathfinder" in the press. He got wealthy during the California gold rush of 1849 and was later elected California's first governor. In 1856, he ran for president as the first candidate of the new Republican party and carried much of the North but lost the election because the Know Nothing Party took a lot of the anti-Democrat vote from the Republicans.
Near the outset of the Civil War, Fremont was appointed a Union general commanding the Department of the West headquartered at St. Louis. Frank P. Blair, Jr., a U.S. congressman from the St. Louis area, had supported his appointment, but it didn't take long for the two men to be at odds. Blair and others criticized Fremont for not reinforcing General Nathaniel Lyon prior to the Battle of Wilson's Creek fought on August 10, 1861, and Blair and Fremont also had some personal disagreements. Then in late August, Fremont angered President Lincoln when he issued his infamous decree emancipating Missouri's slaves and declaring martial law in the state. Lincoln ordered the edict rescinded, but the relation between the two men was already strained. Next, Fremont had Blair arrested for insubordination. (Blair was a military officer under Fremont's command as well a congressman.) This, of course, further strained the relations between Fremont and Blair, who had already been working for Fremont's removal. In fact, that's partly why Fremont had him arrested. Perhaps the last straw, though, was Fremont's failure to reinforce Colonel Mulligan prior to or during the Siege of Lexington, the same way he had failed to reinforce Lyon. After Mulligan was forced to surrender to General Sterling Price and the Missouri State Guard on September 20, Lincoln ordered Fremont to "repair the disaster at Lexington without loss of time," but as far as Fremont's future as commanding general of the Department of the West was concerned, the damage had already been done.
Fremont did set out to try to atone for the Lexington defeat by personally taking to the field, amassing a large army, and forcing Price to evacuate Lexington. Fremont pursued Price into southern Missouri during October of 1861. On October 25, Fremont's body guard, led by Major Charles Zagonyi, chased a few hundred Missouri State Guard troops out of Springfield, and a few days later Fremont and his entire army occupied Springfield. Price and the large portion of his State Guard troops, were camped around Neosho, where Governor Claiborne F. Jackson's government-in-exile voted to secede from the Union. Near the end of October, Fremont and Price entered into negotiations concerning the treatment of prisoners and other matters. They signed an agreement on November 1 that said, among other things, that citizens would not be arrested or mistreated merely because of their political sentiments, as long as they were peaceable citizens who were minding their own business.
The very next day, however, Fremont received word that he had been relieved of duty by President Lincoln. At Springfield, Fremont issued a farewell address to his troops, many of whom were very loyal to him and very upset by his removal. In fact, some of the troops (Zagonyi's body guard, for example) were shortly afterwards mustered out of service because they were considered too personally loyal to Fremont instead of to the Union cause.
General David Hunter was appointed to take Fremont's place, and Hunter declared that he would not recognize the Fremont-Price agreement. That, too, hardly mattered, however, since Hunter and all the Federal troops were soon ordered to evacuate Springfield and fall back to Rolla and Sedalia (places that had rail service).