The Borealis, referred to as Twin Cities–Milwaukee–Chicago (TCMC) during planning, is an Amtrak inter-city rail service that operates daily between Chicago, Illinois, and Saint Paul, Minnesota, via Milwaukee, Wisconsin.

The train supplements the long-distance Empire Builder, serving the same stations but with higher reliability and complementary departure times.

As an extension of an existing Chicago–Milwaukee Hiawatha train, the Borealis doubled Amtrak service frequency between Milwaukee and Saint Paul.

Prior to Amtrak, private railroads ran passenger service between the Twin Cities and Chicago on several corridors.

The Chicago, Burlington and Quincy Railroad (CB&Q) operated a more westerly Twin Cities–Chicago route via Savanna, Illinois.

[4]: 158  The tri-weekly North Coast Hiawatha began operating on June 14, 1971; it was combined with the Empire Builder between Minneapolis and Chicago.

[10] Based on the favorable ridership and revenue projections MnDOT led a Phase 1 study in cooperation with WisDOT, IDOT, the Ramsey County Regional Railroad Authority and the FRA to analyze service alternatives, infrastructure upgrades and anticipated costs.

The Phase 2 study was led by WisDOT to complete the environmental review and prepare a Service Development Plan.

[20] In a February 2024 update, WisDOT announced that the service would be named the Borealis instead of the Great River, and that the train would use refurbished Horizon railcars.

Early demand for the Borealis prompted Amtrak to consider adding a third daily round trip on the corridor.

In May 2024, one Hiawatha round-trip was extended to Saint Paul as the Borealis, restoring two daily round trips to the corridor.

[30] Through the federal Corridor ID Program, a second Chicago–Twin Cities route that includes Madison and Eau Claire is being studied.