https://en.wikipedia.org/wiki/Waukesha,_Wisconsin#Demographics

As of the census[2] of 2010, there were 70,718 people, 28,295 households, and 17,506 families residing in the city. The population density was 2,850.4 inhabitants per square mile (1,100.5/km2). There were 29,843 housing units at an average density of 1,202.9 per square mile (464.4/km2). The racial makeup of the city was 88.1% White, 2.3% African American, 0.4% Native American, 3.5% Asian, 3.5% from other races, and 2.1% from two or more races. Hispanic or Latino of any race were 12.1% of the population.

I think we know the why...