High Quality Content by WIKIPEDIA articles! Southwest (SW or S.W.) is the southwestern quadrant of Washington, D.C., the capital of the United States, and is located south of the National Mall and west of South Capitol Street. It is the smallest quadrant of the city. Southwest is small enough that it is frequently referred to as a neighborhood in and of itself. However, it actually contains five separate neighborhoods.the Southwest Federal Center, also called the Southwest Employment District, is the area between the National Mall and the Southeast/Southwest Freeway (Interstate 395).