Thomas Andrus is believed to be the first settler in the community he named Cass. Thomas first arrived in Chicago in 1833 where he held various jobs, including work on the Illinois and Michigan Canal. He returned to Vermont and came back to the Chicago area in 1835. His first wife Philena Fox with whom he had two children (Mary and Elizabeth) died in 1828. While in Vermont, he married his second wife Melissa Snow Bartlett who accompanied him when he returned to the Chicago area. They had three sons Edgar Smith, Charles William, and Elbridge Gary.

An astute businessman, Thomas established an inn/tavern on his 17 acre farm about 20 miles from Chicago along a busy stage coach line. The farm was located along, what is now the South Frontage Road of 1-55 between Cass Avenue and Lemont Road. The stage coach route followed what would become Route 66. Andrus contributed much to the growth of Cass. He served as a Justice of the Peace, County Commissioner, town Clerk and Assessor. As the community developed, it needed a post office. Once again Thomas filled the need using his inn as the office and serving for 15 years as the Postmaster. Before the post office could be established the community needed a name. Andrus called the community Cass. Thomas also helped establish the Cass Methodist Episcopal Church. Thomas died in 1888; Melissa died in 1883.

Thomas and Melissa’s son Edgar was born in 1835 and is reported to be the first child born in Downers Grove Township. He is said to have to have assisted his father by riding a horse to the Illinois and Michigan Canal which he would swim across to collect the mail. Their second son Charles William served in the 33rd Illinois Infantry during the Civil War. A member of the Andrus family still maintains the Cass Cemetery along Frontage Road.