The front half of Portland’s Masonic Temple on Congress Street is heading for the auction block in September, with close to 50,000 square feet of commercial office space and some retail space available.

“This is a very hot market,” said Thomas Saturley, the president of Tranzon Auction Properties, the auction company offering the sale. “I do sales all over the country, but Portland is one of the best markets right now.”

Built in 1911 and listed on the National Register of Historic Places, the building at 415 Congress St. is split into two parts:

The front half of the building comprises office and retail space, including the Maine attorney general’s Portland office, the office and team store for the Maine Red Claws and Bayside Print Services.

The back half of the building, which houses the original Masonic Temple and banquet space, is not for sale.

According to records in Portland City Hall, the properties are two distinct parcels although they are commonly referred to as one building.

The building’s owner, Kevin Mattson, said that Portland’s recent spark in redevelopment inspired him to consider selling 415 Congress St. Mattson is the president of Dirigo Capital Advisors, a commercial real estate company that buys older and historic properties to redevelop and modernize them. Although the company is headquartered in Hallowell, it maintains an office out of 415 Congress St.

The firm recently bought the former MaineGeneral hospital buildings in Augusta and is in the process of a $23 million redevelopment of them. Mattson said his company no longer has the capability to focus on both the hospital project and 415 Congress St.

“Portland is at an apex,” Mattson said. “We sat in the building for 10 years, and I never would have thought that the old Portland Press Herald building would turn into a hotel or that businesses along Congress Street would pop up.”

The building’s main tenant, the Norman, Hanson & Detroy law firm, is moving to a new location in November after 40 years at 415 Congress St. Mattson said that will open the space for a new purpose.

“415 (Congress St.) needs a developer that can focus on it,” Mattson said.

Although his company has sold close to $25 million in other properties this year, it has never sold property via an auction.

Mattson, who worked briefly as an auctioneer, said that auctions are usually reserved for liquidated properties or estate sales. He decided to go that route rather than a conventional sale, noting that “it’s a gamble. But, we’ll see if it’s the right thing to do.”

Hannes Combest, chief executive officer of the National Auctioneers Association, said that auctions for privately owned commercial properties are becoming more common.

“It is growing and we’re seeing more real estate sold by auction,” Combest said. “It used to be foreclosures, celebrities’ (properties), etc. and now we’re seeing a lot more commercial real estate and residential properties going to auction.”

There are currently 70 commercial auctions with sale listings in 19 states on Tranzon’s website. Of those, five are in Maine – including 415 Congress St. Most of the listings are for self-storage facilities.

Combest said that auctions are ideal for people who want to dispose of assets very quickly and in a more transparent process.

Also, in a strong market, auctions are appealing because there is no lengthy closing process and properties are sold the same day.

“There is an explosion of growth in Portland and an auction can be frothy,” Mattson said.

While the auction house has not yet decided the building’s starting bid, the estimated value of the parcel is $3,497,000, according to city assessor’s records. Records show it was last sold in 2004 for $3 million and in 1996 for $1,525,000.

“It’s an opportunity for bidders to competitively bid,” Saturley said of the auction, adding that he is still meeting with potential buyers to gauge the market value. “It doesn’t matter where it starts, it matters where it ends.”

Saturley said he has given up trying to guess what a property will sell for and that it’s always a surprise.

“That’s the beauty of auctions. You don’t know what it will sell for,” Mattson said, adding that he hopes to gain a profit on the $3 million he spent to buy the building in 2004.

The auction is scheduled for Thursday, Sept. 18. Saturley said the listing has been popular, catching the attention of buyers from Boston to New York.

“It doesn’t surprise me that lots of businesses and entities would like to own a piece of Portland,” Saturley said.

Mattson said he’s hoping a buyer for 415 Congress St. will think of innovative ways to maintain its history.

“It’s a remarkable old building,” Mattson said. “I hope whoever buys it can keep its historical significance.”