WASHINGTON — In the six months since a court allowed the Corcoran Gallery of Art here to dissolve, a victim of financial struggles, about 17,000 works in the museum’s overall collection — by masters like Degas, Sargent, Albert Bierstadt and Cy Twombly — have been in a highly unusual institutional limbo. Their fate is being adjudicated by a group of veteran curators from the National Gallery of Art, which agreed last February to bring as many Corcoran pieces under the museum’s own roof as appropriate and to help find homes for others in Washington-area public collections.

On Thursday, the National Gallery announced that almost 6,500 works had been taken into the overall collection so far. The museum’s holdings of 1,215 American paintings alone will grow by 226, including beloved works like Frederic Edwin Church’s 1857 “Niagara,” a 7 ½-foot-wide blockbuster that Nancy Kay Anderson, the curator of American and British paintings at the National Gallery, refers to as “our ‘Niagara problem” because it is so important and so large that paintings at her museum will almost certainly have to move or go into storage to accommodate it. The process that has been underway behind closed doors at the National Gallery — one large museum essentially digesting another of considerable size — is, in its scope and particulars, unlike anything an American museum has undertaken before.

While some curators are still months away from making final decisions, the sheer number of works chosen by the National Gallery so far is staggering. The additions will be transformative, particularly enhancing the museum’s reputation for American art, and they will fill in historical gaps elsewhere. Among the firsts for the National Gallery collection are two bronzes by Frederic Remington, an important work by the sculptor Hiram Powers and work by Betye Saar, the Los Angeles artist. But there are also works being turned away, like a George Peter Alexander Healy portrait of President James Buchanan, which curators said would be better served at the National Portrait Gallery.

“There’s really no model for this,” said Judith Brodie, the National Gallery’s curator of modern prints and drawings, whose task of sorting and deciding is numerically the biggest because of the size of the Corcoran’s collection of works on paper. She called her list “the Bible” — a weighty compendium of some 9,000 prints and drawings amassed over more than a century before the museum closed its doors last year.