The historic James L. Clemens House in north St. Louis was destroyed by a fire early Wednesday morning.

Firefighters say the St. Louis landmark, located at 1849 Cass near the intersection of Helen and Mullanaphy, caught fire around 3:30 a.m.

Scene photos: Fire at historic James Clemens House

Samuel Clemens (Mark Twain) was James Clemens Jr.’s nephew and was said to have visited the house on several occasions, according to the City of St. Louis website. The house was built in the mid-1800s and was made a City Landmark in 1971.

“I'm sickened by this,” said Michael Allen, an architectural historian at Washington University. “Something that's a huge part of our architectural and cultural heritage seemingly gone forever now.”

Allen said the home is a symbol of the city’s heritage.

“It's famous for its ties to the early iron industry, which gave rise to St. Louis's manufacturing might in the 19th Century.”

The home may have become a city landmark in the 1970s, but in recent years, it had been vacant.

“There's a part of me that's not surprised at all. This was a long-time coming and the current owner did nothing really to prevent this,” Allen said

The current owner of the Clemens House is developer Paul McKee, who owns more than 100 buildings in North St. Louis. He said he spent “six figures” shoring up the 160-year-old building, saving the facade and securing it.

“We are constantly boarding them up and if you pay attention to the homeless, we put the boards up, they tear them down,” McKee said.

St. Louis Firefighters may never know who or what caused the fire, as the building is too dangerous for investigators to enter.

“We've done the best we could," McKee said. "Nobody else is stepping up to buy old buildings on the north side other than this lady and I. we bought it to preserve it. We've done the best we could to preserve it. We welcome anyone else who thinks they can do a better job.”

McKee added that he will look into whether any elements of the building can be salvaged.

Facebook Live: Historic James L. Clemens House catches fire

At least two other buildings were damaged by the fire.

PHOTOS: Historic photos of Clemens House