Most U.S. residential land is zoned single-family-only, prohibiting duplexes, ADUs, and apartments. Zoning reform proposals — implemented at the state level in Oregon (HB 2001), California (multiple bills), Minneapolis, and elsewhere — legalize "missing middle" housing, eliminate parking minimums, and override local exclusionary zoning.
Defenders of reform ("YIMBY" — Yes In My Back Yard) argue that artificial supply restrictions cause the housing affordability crisis. Defenders of existing zoning argue local control protects neighborhood character, schools, infrastructure, and home values.
Federal involvement is limited but growing: HUD's "Affirmatively Furthering Fair Housing" rule, conditioning some federal grants on local zoning reform.