ROSEMONT, IL - SEPTEMBER 22: Bed Bug Central public relations associate Calvin Allen shows a vial containing live bed bugs at the Bed Bug University North American Summit 2010 on September 22, 2010 in Rosemont, Illinois. The two-day conference of bed bug experts and pest control workers featured seminars from researchers and vendors displaying the latest products focused on bedbug detection, elimination and prevention. (Photo by Brian Kersey/Getty Images)
The Maryland city moved up nine spots from its ranking last year.
Washington, D.C., Chicago, New York City and Columbus, Ohio, rounded out the top five.
Atlanta (No. 16); Charlotte, North Carolina (No. 19); Boston (No. 28); Dayton, Ohio (No. 32); Seattle (No. 34); Orlando (No. 44); and Miami (No. 46) made the top 50.
The cities were ranked based on treatment data from the metro areas where Orkin performed the most bedbug treatments from Dec. 1, 2015, to Nov. 30, 2016.
"We have more people affected by bedbugs in the United States now than ever before," Orkin entomologist and director of technical services Ron Harrison said. "They were virtually unheard of in the U.S. 10 years ago."
Orkin calls bedbugs "hitchhikers" that travel from place to place.
Orkin officials think bedbugs have become prevalent because they've built up a resistance to chemicals.
They also said you might not know you have bedbugs because many people don't have a physical reaction to the insect's bites.