The event is organized by the Patuxents to raise money for the Friends of Fort Frederick State Park. It is intended to give visitors a chance to experience life as it was on the frontier from 1640 through 1840.
The Patuxents is a 40-member re-enactor group that portrays a former Calvert County, Md., Indian tribe.
"People should be more aware of history," said Mark Thomas, one of the sutlers at the market. "The whole fort and park should all look at it from the historical value, because that's what it is."
Thomas is an 18th and 19th Century gunmaker and engraver from Dayton, Va. He said he travels several times a year to various colonial fairs and has been a Patuxent group for about 20 years.
Jeff Welch, a Patuxent from Charles Town, W.Va., said the fair gets bigger every year.
He's expecting about 1,700 participants, including about 160 sutlers. Thousands more are expected to visit the fair this weekend. The event started in 1995 with about 800 participants.
He said re-enactors and spectators come from all over North America, including Canada, California, Arizona and Florida.
"This will be the biggest ever," Welch said. "People that travel all over the country said this is the best to come to."
The Patuxents have already begun planning next year's fair, he said.
"You're thinking about it all year long to make it better," Welch said.
Welch said one of the reasons the Fort Frederick event is so popular is its strict rules. Sutlers are voted in according to the description and pictures they provide the Patuxents.
He said all of their items must be identical to colonial products with no resemblance to the modern era.
Among the items for sale are sheepskin, leather bags, cowhides, pewter jewelry, tents, moccasins and muskets.
"We do this for a living," said Charles Chapman, of Sparta, Tenn.
Chapman and his wife, Susan, run a shop called Luck O'th Irish. Both were decked out in colonial garb.
He said they travel to different fairs along the East Coast.
Charles Chapman said not only does their shop sell a selection of frontier goods, but they recount the history of the era to interested visitors.
"We will share historical information with them to fully enjoy and take advantage of the event," he said.
"There's lots of information here and lots of wonderful people," Susan Chapman said.
Fred Threlfall, of Captain Pipe Presents the Honest Brothers, of Pittsburgh, Pa., has been a sutler at Fort Frederick for the last three years. Threlfall, an artist and historian, runs the business with Ken Gahagan, a knifemaker, and David Hughes, a silversmith.
"There are good people here that are interested in our early history," he said. "The fair was a big thing in this time."
Fort Frederick was built in 1756 by the Colony of Maryland to defend its Western frontier during the French and Indian War. It has been partially restored and is considered the best-preserved, pre-Revolutionary War stone fort in North America, according to the Maryland Department of Natural Resources Forest and Park Service.
During the Revolutionary War, the fort served as a prisoner of war camp for Hessian and British soldiers. During the Civil War, companies of the 1st Maryland Infantry occupied the fort to guard important points along the Potomac River.
The event will continue today and Saturday from 10 a.m. to 5 p.m. and on Sunday from 10 a.m. to 3 p.m. Admission is $3 per person and free for children under 6 years old.
Fort Frederick State Park is one mile off Interstate 70, Exit 12 (Maryland 56), 20 miles west of Hagerstown.