Galesburg Police were called to the American Legion in Galesburg for what witnesses described as a suspicious incident on Friday.
Officers made contact with a man who said he arrived to work at the site, in the 500 block of East North Street, and spotted a black Mitsubishi Lancer.
The witness said he believed the man and woman seen in the vehicle were allegedly engaged in a sex act.
A second witness at the American Legion said he saw the same vehicle earlier in the morning. He was also able to recognize the victim, whom he allegedly described as being underage.
Police were able to interview the victim as well as a friend who told police the victim had allegedly slept with a 25-year-old man.
But using the information, officers were able to locate what turned out to be 34-year-old Andrew Cunningham, of Connecticut, at a Super 8 in Knoxville.
The victim was taken to an area hospital for a medical evaluation.
Cunningham was arrested without incident and is being charged on felony counts of aggravated criminal sexual assault in the case.