Gordon, 24, who was taken into custody Tuesday night, did not enter a plea during his first court appearance. He is scheduled to appear before the judge again on May 18.
Gordon is charged with first-degree murder and armed criminal action in the death of Clark, a sophomore engineering student at Southern Illinois University-Edwardsville. He does not have an attorney.
Florissant Police Capt. Tim Fagan, the deputy commander of the Major Case Squad of Greater St. Louis and lead investigator in the case, said police arrested Gordon after his name was found in emails Gordon traded with Clark about the car Clark was trying to sell. Investigators said the two did not know one another before they met.
Police say Gordon is an employee of a truck driver training center in the St. Louis suburb of Hazelwood, Missouri, not far from where Clark's 2007 Nissan 350ZX and body were found Tuesday. It was not immediately clear whether Gordon has an attorney.
Clark, who is from the southwestern Illinois town of St. Jacob, was reported missing by family members on Monday. Authorities say he was last seen by his girlfriend.
"Our hearts and minds are with Taylor Clark's family and friends as they cope with this tragic loss," SIU-E Chancellor Julie Furst-Bowe said in a statement issued Wednesday. "At a time of the year when the new spring season brings the promise of brighter days ahead, and commencement provides unending potential for so many of our students, it is truly sad that Taylor had his bright future taken away."
The Belleville (Illinois) News-Democrat reported that Clark worked at a convenience store in Troy, where a candlelight vigil was scheduled for Wednesday night. A similar vigil was held Tuesday night on campus.
Clark's death comes during the same week as a Monday court hearing in St. Charles County in which a 23-year-old man was sentenced to life in prison for fatally stabbing a 45-year-old St. Louis man during an encounter and planned robbery in 2012 that was set up through a Craigslist ad.
On the same day of the hearing, Fairview Heights, Illinois, police unveiled a "safe exchange zone" on its parking lot, complete with security cameras, to help citizens safely broker online transactions with strangers.
"You never know who it is you're contacting," Fagan said. "Precautions should be taken."
The Associated Press contributed to this report. All rights reserved.