Effective January 1, 1921 the City of Detroit renumbered its street addresses. The Federal Lithograph Company with Frischkorn Real Estate Company produced this map to explain the numbering changes. Notably, the numbering on Grand Boulevard and in the Grosse Pointes, River Rouge, and Oakwood (later annexed) did not change.
Detroit had not yet annexed all of its current land, so you can still see Redford Township and Dearborn Township on Detroit’s present day Westside. Rouge Park only appears as “Detroit City Park” and Outer Drive is noted along its proposed route. Frischkorn Real Estate speculated to acquire land the along Warren Avenue in future Detroit. They later sponsored the Grandale and Grandale Gardens (Redford) developments just south of the “Russell Municipal Aviation Field.” I previously thought this was the current Aviation Subdivision, but that is further south and along the Detroit/Dearborn border.
Another oddity on this map that I think I got wrong before is that this map includes both Hamtramck city and Hamtramck Township. The northern sliver that was left of Hamtramck Township was annexed by Detroit just two years later in 1922.