With the addition last week of 12 properties, including the Kennebec Arsenal in Augusta and the Stevens School in Hallowell, more than 100 sites have been included on the list of the state’s most endangered historic properties since its inception.

Maine Preservation, the independent nonprofit organization that started the list in 1996 and adds properties each year, says 41 of the sites have been saved. Work at some level is under way at 19 of the properties — labeled as “in motion” on the list — and 18 remain threatened. Fifteen that were placed on the list could not avoid the wrecking ball, including the China Masonic Hall in China and the Kennebec County YMCA in Augusta.

There are lessons to be learned from the properties that have survived, as well as the ones that have been lost. In general, it takes the right ownership and a viable economic strategy to save an endangered historic property. It also takes community support, persistence and good timing.

Ultimately, in most cases the work is worth it. The saved properties have become home to local organizations and businesses, and a point of pride for their communities.

The past should not be preserved just for preservation’s sake. Properties with real historic value, however, should not be razed because of a momentary lack of care or effort, or because of circumstances that can be controlled with the right policies.

One victory on the list is Pennell Institute in Gray. The clock-towered building, a former school that dates to 1876, was slowly crumbling when a community-wide renovation effort began. With all new insides, it is now home to the municipal offices.

Similar groundswells of support saved the former Central Fire Station near downtown Saco and the Bar Mills Elementary School in Buxton, a rural community west of Portland. Both seemed destined to become parking lots until residents protested. The fire station is being developed into senior housing, while the school now houses the local historical society.

Sometimes, the economic situation of a building overwhelms other considerations. The former YMCA in Augusta was demolished in 2011 after its owner said he could not come up with a feasible redevelopment plan or find a buyer. The razing came three years after the owner first applied for a demolition permit, and after the Augusta Historic Preservation Commission spent about $10,000 heating the building, hoping to delay its final fate.

The future of two other central Maine properties is up in the air. The Colonial Theater in Augusta, added to the list in 2011, remains threatened, though a nonprofit organization has been working for two years to save the building. The Hains building in Waterville, added last year, remains vacant but is receiving marketing help from city organizations.

Both state and federal tax incentives are in place to help make the renovation of historic buildings more attractive to developers. Maine Preservation says those incentives have led to $273 million in investment since 2008. Communities also can receive a designation through the Maine Historic Preservation Commission that can open the way for grant funding. Gardiner is one of 10 Maine municipalities to do so.

The commitment of community members to a particular endangered building, however, is most important. Someone has to shepherd the process through, and make sure the properties don’t deteriorate past the point of no return in the meantime.

As Earle Shettleworth Jr., the state historian, told the newspaper this week, “Buildings don’t save buildings. People save buildings.”