Lewis Winans Ross was an Illinois attorney, merchant, and U.S. Representative from Illinois's 9th congressional district. He was widely known as an antiwar Peace Democrat or Copperhead during the American Civil War.

The 9th congressional district of Illinois covers parts of Cook, Lake, and McHenry counties as of the 2021 redistricting which followed the 2020 census. It includes all or parts of Chicago, Evanston, Glenview, Skokie, Morton Grove, Niles, Northfield, Prospect Heights, Wilmette, Buffalo Grove, Hawthorn Woods, Wauconda, Island Lake, Long Grove, Lake Barrington, Algonquin Township, Cary, Crystal Lake, Lake in the Hills, Lakewood, Oakwood Hills, Trout Valley, Algonquin, Port Barrington, Barrington Hills, and Fox River Grove. It is anchored in Chicago's North Side, along Lake Michigan, and covers many of Chicago's northern suburbs. Democrat Jan Schakowsky has represented the district since January 1999.