Embassy Row is the informal name for a section of Northwest Washington, D.C. with a high concentration of embassies, diplomatic missions, and diplomatic residences. It spans Massachusetts Avenue N.W. between 18th and 35th street, bounded by Scott Circle to the south and the United States Naval Observatory to the north; the term is often applied to nearby streets and neighborhoods that also host diplomatic buildings, such as Kalorama. Of the 177 diplomatic missions in the city, the majority are located on or near Embassy Row, including those of Italy, Australia, India, Greece, Egypt, Ireland, Japan, and the United Kingdom. Due to the large number of well-preserved Gilded Age estates and townhouses, many of which house diplomatic missions or dignitaries, Embassy Row has been protected as part of the Massachusetts Avenue Historic District. Its historic and multicultural character has also made the area a center of tourism and local cultural life. History 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. Consequently, the segment between Scott Circle and Sheridan Circle gained the nickname "Millionaires' Row". The Great Depression of 1929 led many to sell their homes; the often illustrious and expansive estates were well-suited for housing diplomatic missions as well as lodges of social clubs, giving Embassy Row its present name and identity. The relocation to Embassy Row of diplomatic representations, many of which had been established in Meridian Hill in previous decades, was further catalyzed by the construction of the British Embassy, commissioned in 1925 and completed in 1930, and the Japanese Embassy, built in 1931. The greatest number of embassies and chanceries moved to Embassy Row and the neighboring Kalorama neighborhood in the 1940s and early 1950s. On the southeastern section of the row, between Scott Circle and Dupont Circle, many individual houses and 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, which has occasionally been referred to as Think Tank Row. 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