The system’s 2.1-mile (3.4 km)[5][3][6] original “M” line connects the Milwaukee Intermodal Station and Downtown to the Lower East Side and Historic Third Ward neighborhoods.

[7] On April 11, 2024, a 0.4-mile (640 m) Lakefront, or “L” line,[5] to the nearly complete high-rise development The Couture, began offering full daily service.

[9][10][11] After World War II, the federal government invested heavily in the development of an interconnected interstate highway system, and raised taxes on private railway and streetcar operators.

[16] The Hop's construction came in the wake of a failed plan to build a light rail system in the Milwaukee area.

In 1997, the region was awarded $289 million after local leaders created a plan to build a light rail system, expand Interstate 94, and increase bus service in Waukesha County.

[18] However, Republican leaders and Governor Tommy Thompson backtracked and banned use of the funds for a light rail system.

[25] In mid-April 2016, the city invited bids for the construction of the project's first phase, with a June 1 due date for proposals.

[26] On August 19, 2016, Omaha contractor Kiewit Infrastructure was announced as the winning bidder for the contract to construct the line and carhouse.

[14] In October 2017, it was announced that a 12-year sponsorship deal, including naming rights, had been reached between the Potawatomi Native American community and the city of Milwaukee.

[46] Two additional extensions are being planned: one north past Fiserv Forum into Bronzeville and the second as a new branch from the Third Ward and extending south to Walker's Point.

[47][48] A portion of the northerly M-line extension was originally planned to be operational in time for the 2020 Democratic National Convention.

[49] Since the 2020 Democratic National Convention ultimately became a virtual event due to the COVID-19 crisis, the short term need for the partial extension became moot.

[8] Fare-free service originally planned to end after one year is still in effect due to delays in procuring a fare sale/validation system.

[54] The system's car house, its storage and maintenance facility, is on Vel R. Phillips Avenue (4th Street), under an elevated section of the I-794 freeway.

[14] On April 6, 2015, the city invited bids for the supply of four streetcars, with the issuing of a request for proposals to interested manufacturers.

[55] In November 2015, the city awarded an $18.6-million contract to Brookville Equipment Corporation to build four "Liberty" model streetcars for Milwaukee.

The first of the five vehicles arrived in Milwaukee from Brookville on March 26, 2018,[59] and made the first test run over a short section of the line on April 11.