The first white settlers arrived in the vicinity about 1833 or so, and the first settler on the actual site of present-day Quincy came several years later. In the early and mid 1840s, the place was known as Judy's Gap, because a man named Samuel Judy had a blacksmith shop there. The date when the town was surveyed and platted is not known for sure, although one report places it as 1848. At that time, the community was given the name Quincy, reportedly after former President John Quincy Adams, who had died earlier the same year.
In the early to mid 1840s, while still known as Judy's Gap, the place played a minor role in the so-called Slicker War or Turk-Jones feud of that era, because it and its immediate environs served as somewhat of a gathering place. For instance, one of the very first incidents of the feud happened at Turk's tavern just north of Judy's Gap.
Quincy was also the site of a few minor skirmishes and other incidents during the Civil War. One, in particular, that I know about occurred on September 4, 1863, when a band of men under a notorious guerrilla leader named John Raftre (aka Rafter) dashed into the town and immediately started shooting up the place.
Raftre had been known in the area of southeast Henry County, northeast St. Clair, southwest Benton, and northwest Hickory since at least March of the previous year, when he was reported killed in a skirmish with Federals southeast of Leesville near the Henry-Benton County line. Reports of Raftre's demise, however, were premature. In January of 1863, he was spotted prowling about Clinton, Missouri.
Then eight months later, he came charging into Quincy and started shooting at some citizens sitting in front of a store. One man was killed, and the others scattered. The guerrillas then turned their attention to four soldiers of the 18th Iowa Volunteers, who had just arrived on a stagecoach and taken shelter in one the houses in the town. Raftre and his men followed them to an upstairs room and took them prisoner, then plundered the few businesses in town and were in the act of setting the whole place on fire when the 8th Missouri Militia Cavalry came galloping into town, opened fire, and scattered the bushwhackers. Raftre was killed in the skirmish, and this time he didn't come back to life. The Federals also succeeded in regaining possession of some of the plunder that had been taken from the stores and citizens.
The remaining guerrillas herded the soldiers they had captured along with them as they made their escape, and, no doubt in retaliation for the death of their leader, killed the prisoners not far outside town. Presumably all four of them were killed, although only two bodies were found in the immediate aftermath of the incident.