The Museum of the American Revolution, whose building at Third and Chestnut Streets has been under construction for two years, plans to announce Thursday that it will open its doors to the public April 19, 2017 - the 242nd anniversary of the battles of Lexington and Concord, considered the opening of hostilities between Britain and its North American colonies.

When the smoke cleared following those nasty Massachusetts skirmishes so long ago, 122 fighters on both sides had lost their lives, and the colonies were launched on a revolutionary road that would not reach the goal of independence for eight arduous years.

In addition to announcing an opening date, museum officials also reported that a donation of $10 million has been made by H.F. "Gerry" Lenfest, the largest contributor to the museum and the former owner of the Inquirer, Daily News, and Philly.com.

Lenfest has already donated a $40 million matching grant to the museum, in addition to earlier support of about $9 million.

His latest contribution of $10 million also comes in the form of a matching grant. For every dollar the museum raises independently, Lenfest will pair it with another dollar.

On numerous occasions, Lenfest has said that he considered the museum the "missing link" that would tie together Liberty Bell, Independence Hall, National Constitution Center, other National Park Service sites, and area battlefields.

Museum officials say their $120 million construction project will throw open the doors in April without long-term debt.

"Currently, we have raised $130 million, not including the new challenge," said Michael Quinn, the museum's president and chief executive. Fund-raising is now focused on increasing endowment.

"We're building a robust fund-raising capability," Quinn said, citing 10,000 supporters already on the rolls and a membership program set to start in September - about the time administrative and curatorial staff is able to move into the new redbrick building, designed by Robert A.M. Stern Architects.

"We're really in the homestretch," Quinn said.

It has certainly taken a very long time to reach this point.

Initially, the museum, which is steward of the Valley Forge Historical Society's trove of more than 3,000 Revolutionary War-era artworks and artifacts, including the field tent made for Gen. Washington during the hard Valley Forge winter of 1777-78, wanted to locate on land at Valley Forge National Historical Park.

But a prolonged effort to build a massive museum and conference center there produced endless disputes with local residents and officials.

In 2009, museum backers reached a deal with the National Park Service to swap the land at Valley Forge for the Chestnut Street site, then occupied by the old Independence National Historical Park visitor center.

It has taken far longer to site and build this museum than it did to fight the war for independence it celebrates.

"We're about 75 percent done," Quinn said last week during a walk through the construction site. "We'll be occupying the building in September, and then there will be six months of frenetic activity. We'll have six months to install all the exhibitions, the electronics, the software, the hardware, get it all working, bring in the objects, and then throw our doors open on the 19th of April."

At this point, with September three months away, the interior of the museum is fleshed out, if lacking finish, such as terrazzo flooring and stone walls. The ground-floor orientation theater, which will seat about 190, is completely blocked out and ready for raking.

Sweeping, curved stairs, which will be flooded with natural light, are in place. They will draw visitors up to 16,000 square feet of gallery space on the second floor, now strewn with crates, coils of cables, stacks of plywood, and other construction flotsam.

Visitors will traverse an arc of galleries that lead chronologically through the revolution, from its beginnings in disgruntled Boston to its conclusion on the fields of Yorktown and beyond, to the treaty of Paris and the writing of the U.S. Constitution in Philadelphia.

The dramatic highlight of this presentation will be a full gallery for display of the museum's most intriguing artifact - Washington's field tent.

The unprepossessing tent will be completely sealed within its own enormous gallery space in a totally controlled environment. Visitors will enter one half of the gallery to view the tent through a glass wall. What has been called the first "White House" (a kind of age-flecked gray at this point) will be a theatrical star, the focal point of a production watched from the comforts of auditorium seating.

Presentations in other galleries will also take an approach influenced by the entertainment-style flair. In one, visitors will wander beneath a constructed "Liberty Tree" listening to the voices of Boston debating the latest news from the Mother Country. Museum personnel will, perhaps in costume, draw in gallerygoers.

In another room, visitors will be confronted by a surrounding immersive video of British regulars firing at them.

In still another gallery, a full-size privateer ship will present the war on the sea. The ship is now under construction at the Independence Seaport Museum.

"Our challenge is that we have to make this history accessible to people in today's world," said Quinn.

"Our visitor surveys show that Americans know the revolution was an impossible achievement - to win independence, to establish the Declaration [of Independence] and the Constitution as our ideals. Americans want to know, How did that happen?"

ssalisbury@phillynews.com

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