Missing middle housing refers to home types such as duplexes, triplexes, quadplexes, cottage court apartments, townhomes, and other smaller, multi-unit home types. It is “middle” because it occupies an important set of housing options between the single-detached house and the midrise apartment, and “missing” because across most of the United States, including Salt Lake City, they have become an endangered species due to exclusionary zoning rules. These home types used to be legal and can still be found in many older neighborhoods, but became largely illegal to build in the early-to-mid 20th century, as cities sought to segregate people by race and class.