A downtown landmark now sits vacant after the last remaining business with an office there moved out.

Frank Sheffer, who owns the National Bank building at 112 W. Washington St., moved his accounting practice to 1426 Holland Road several months ago. Family members continue to help clean out odds and ends that are left in the building.

“It’s going to be up for sale sometime soon,” said Joe Weintrob, Sheffer’s nephew. He believes the building is exactly 100 years old.

“It’s an old building here,” he said. “I helped build the downstairs office buildings in the late ‘60s. It’s just deteriorated since. The cost of upkeep is too high.”

Weintrob said gas to run the boilers is expensive. In addition, the elevator and roof need repairs, he said.

Weintrob said he hopes the building can soon find a new owner.

“It makes a big blank place downtown,” he said.

The building’s vacancy marks another transition on the historic block that has been in a state of flux for several years.

Across the street, Monument Construction completed a project that put lofts on upper floors of previously vacant commercial buildings and retail space — a barber and a wine and cheese shop — on the ground floors.

It continues in a similar manner with several buildings immediately to the west. But at the end of that side of the block, a vacant commercial building that suffered a fire in 2009 and the former Salvation Army thrift store, vacated by the charity just last year, both are up for sale.

Next to the National Bank building, a building bears a sign reading “East Coast Taco Company,” which a Facebook page for the restaurant indicates will open soon. It previously held a tapas restaurant and, before that, a high-end Italian eatery.

West of that building, a Portsmouth woman is in the process of opening a dance studio.

Most of the rest of that side of the block is occupied by commercial buildings. At the western end is law firm Pender and Coward, which is conducting renovations on a Market Street building with a goal of moving there.