The heart of the neighborhood is Massachusetts Avenue, which in the area of Observatory Circle is mostly lined with embassies. Therefore most of the area is commonly regarded as Embassy Row.
The only residential section of Massachusetts Heights is a small triangular wedge between Massachusetts Avenue and Garfield Street, just adjacent to Observatory Circle and the grounds of the Vice President’s Residence. The remainder of the neighborhood is entirely occupied by the Cathedral and its affiliated properties, including St. Albans School.
Considered Washington’s premier residential address in the late 19th and early 20th centuries, Massachusetts Avenue became known for its numerous mansions housing the city’s social and political elites. The segment between Scott Circle and Sheridan Circle gained the nickname “Millionaires’ Row”.
The Great Depression caused many to sell their homes. The expansive old estates proved well-suited for use as embassies, and also as lodges of social clubs, giving Embassy Row its present name and identity. Some of the avenue’s newer buildings were purpose-designed as embassies, starting with the British Embassy, designed in 1928 by Sir Edwin Lutyens, and the Japanese Embassy, built in 1931.On the southeastern section of the row, between Scott Circle and Dupont Circle, many mansions were replaced by larger office or apartment buildings between the 1930s and the 1970s. More recently, several prominent think tanks have clustered in that area.
Embassy Row is protected as the Massachusetts Avenue Historic District, created in 1974 following controversy about the demolition of historic townhouses on 1722-28 Massachusetts Ave NW. Many of Embassy Row’s diplomatic buildings open to the public once a year in May, an initiative nicknamed Passport DC. This event was started in 2007 by the embassies of member states of the European Union, and extended in 2008 to other countries around the world under coordination by Cultural Tourism DC. Within this program, the EU embassies still open on a separate day, labelled EU Open House. A separate program, the Embassy Series, started in 1994 and coordinates concerts organized in the embassy buildings.