Great Architects of New York: Henry J. Hardenbergh
20 Washington Square North
North side of Washington Square North between Fifth Avenue and Macdougal Street, back to Macdougal Alley.
New York, N.Y. 10011
Greenwich Village
1828-1829; widened and fourth story by Hardenbergh added in 1880
Offices for nonprofit organizations
AIA Guide
On the building overall: "According to the district's Landmarks Preservation Commission report, Nos. 1-13 are 'the most imprtant and imposing block front of early Nineteenth Century town houses in the City [sic].' Nos. 19-26, a Greek Revival group that includes an unusual large town house in the Federal style (No. 20), is not far behind. When built, they housed New York's most prominent merchant and banking families and, over time, other distinguished individuals."
On the rear alley: "This charming cul-de-sac (less charming when filled with residents' cars) is jointly owned by property holders on Washington Square North and on the south side of 8th Street. The 20-story bulk of No. 2 Fifth Avenue looms over it, overwhelming its space and diminishing its small-scaled delight."
Landmark Status
This building is within the Greenwich Village Historic District, designated by the City in 1969, by the Federal government in 1979.

Tradmark early Hardenbergh shows through in this renovation. Look at the basement and fourth-floor window lintels and arched main entrance. Similar designs are visible at the early and the later batches of the West 73rd Street rowhouses.

"Unusual" is the word for it, though. Why does the column of windows at left put so much distance between itself and the rest of the building? (This must be the part that Hardenbergh widened.)

South facade, facing Washington Square.

North facade, facing Macdougal Alley.