Overcrowding was such a problem that several Black schools held double shifts where the school population was divided in half and attended only half-days of school. However, in 1961, the Urban League published a report that found 382 classrooms were vacant in Chicago Public Schools, despite significant overcrowding in majority Black schools. Further, it reported that majority Black schools received only two-thirds of the funding that white schools received and that 70 percent of all students on double shifts were Black.
Rather than spending money to increase the capacity of overcrowded schools or redrawing the district borders to allow the schools to integrate, the Board of Education approved Willis’s plan to purchase the 20-by-36-foot mobile school units and park them outside of school buildings to use as overflow classrooms. These were the structures that activist Rosie Simpson would come to name “Willis Wagons."
Initially, the trailers were proposed as a temporary fix. However, under Willis’s supervision, they became an indefinite solution—some remaining until the 1990s. In some schools such as Waller High School (now Lincoln Park High School), classes of white children met inside the school building while classes of Black children were forced to meet inside the trailers.
In many ways, Willis Wagons became a potent symbol and catalyst in the struggle against Chicago Public School Board of Education's segregationist policies.
One of the most publicized protests before the 1963 boycott was held in August of that year when activists blocked the installation of a school made entirely of Willis Wagons on a vacant lot in Englewood.