A historic Charleston building exchanged hands in a $3.75 million deal that will bring 100 workers to the downtown area, officials said.

The three-story building at 26 and 28 Broad St. will serve as the headquarters for NCGS Inc., a local clinical medical research firm.

Nancy C.G. Snowden, the company's chief executive, said the two upper levels of the 17,000-square-foot building will house the workers.

"Most of the people are working from home and we need a space to accommodate them and be a centralized operation," she said Friday.

The lower level of the building is planned to house retail space.

NCGS' current headquarters is housed in Snowden's home-office on Society Street.

Snowden, a registered nurse and onetime restaurateur, founded NCGS in 1984. Her company manages clinical trials for pharmaceutical, biotechnology, medical device and diagnostic companies.

The building formerly served as the longtime offices for the Charleston law firm of Young Clement & Rivers, which moved to lower Calhoun Street about three years ago.

The portion of the property at 28 Broad was known as the James Gregorie House. It was built in 1791 and renovated during the 19th and 20th centuries, according to the book "Buildings of Charleston." The other part of the building at 26 Broad was constructed around the same time and was known as the William Rouse building.

Snowden, who has redeveloped numerous historic properties in the downtown area, said she plans to renovate.

"It's got a rich history and it's an important building, so I want to preserve and update it," she said. "A majority of the work is internal, and I'll try to make the rear facade more pleasing since it faces a neighborhood. I'll make it less industrial."

Snowden said construction is scheduled to begin within months and the building should be open by the end of the year.

Snowden, who once owned Carolina's restaurant on nearby Exchange Street, said she plans to rehabilitate more historic structures.

"This will not be the last one," she said. "I have a passion for these beautiful old buildings."

Snowden created a bit of a stir two years ago when she planned to buy an 1840s-era church at 43 Wentworth St. and turn it into residences and office space.

She eventually pulled back on plans and instead agreed to give the Church of the Redeemer a chance to raise money to buy the property at the price she had planned to pay.

That left her "in a position to start her headquarters search over," said real estate broker Mark H. Mizell of Sadler Group of Charleston LLC, who worked with Snowden on the Broad Street purchase.

Reach Tyrone Richardson at 937-5550 or Twitter @TyrichardsonPC.