The district includes west and southwest suburbs of Chicago as far as the DuPage County border, as well as portions of the Southwest Side of the city of Chicago itself, and covers , making it one of the 50 smallest districts in the U.S., although there are five smaller districts in Illinois. It is adjacent to the 1st District to the east and south, the 4th District to the north, and the 11th District to the west, and also borders the 6th and 7th Districts at its northwest and northeast corners respectively. The district was created following the 1830 Census and came into being in 1833, five months before Chicago was organized as a town; it initially included northern and western Illinois before representing areas of east central and northwestern Illinois from 1843 to 1873. The district has included part of Chicago since 1873, and part of the city's southwest side since 1895; the district has been primarily suburban since 1973.