Bus
Ride the free airport train to the Multi-Modal Facility. Buses stop in downtown Milwaukee near the Intermodal Station.
Car
Rideshare is expensive for this distance but door to door; it makes sense for groups.

The Coach USA airport express bus runs from Chicago O'Hare to downtown Milwaukee in about 1 hour 45 minutes for roughly $35–40. Alternatively, take the Blue Line to Chicago and Amtrak's Hiawatha (about 90 min). Uber/Lyft costs roughly $120–180.
Typical cost and journey time from O'Hare into Milwaukee.
Not a practical option for this trip.
The direct bus is the simplest way to Milwaukee: no changes, luggage under the bus. If its schedule doesn't fit, take the CTA Blue Line downtown and Amtrak's Hiawatha from Chicago Union Station (seven round trips a day, about 90 minutes).
Ride the free airport train to the Multi-Modal Facility. Buses stop in downtown Milwaukee near the Intermodal Station.
Rideshare is expensive for this distance but door to door; it makes sense for groups.
The questions people ask most about O'Hare.
Coach USA airport express bus: About $35–40 one way, taking about 1 hr 45 min.
Roughly every 1–2 hours, early morning to late evening.
Designated rideshare zones on the upper level of Terminals 1–3. Expect to pay about $120–180.
O'Hare Multi-Modal Facility — take the free Airport Transit System train from the terminals.