Conversation so far:
What happened in 1961?
In 1961, the Whitney began seeking a site for a larger building. It eventually settled at the southeast corner of Madison Avenue and 75th Street on Manhattan's Upper East Side.
Any notable person in the Whitney Museum of American Art article?
The Whitney Museum of American Art was founded in 1930 by Gertrude Vanderbilt Whitney, a wealthy and prominent American socialite and art patron.
How is the new building for the Whitney Museum of American Art better than the old?
The new building is much more expansive and open than the old ones.

Question: Who built the new musuem?
Self-contained rewrite: Who built the new musuem building for the Whitney Museum of American Art?