While Dunedin's Baldwin Street is now recognised as the steepest street in the world, for much of its existence such recognition went elsewhere. The Guinness Book of Records used to regularly list Filbert Street and 22nd Street in San Francisco as the world's steepest streets, each with a maximum gradient over a short section of 1 in 3.17. That is, for every 3.17 units they go in horizontally, they go up vertically 1 unit.
This was taken as Guinness gospel until people in Dunedin started looking up Baldwin Street in the city's North East Valley and complaining to the book's publishers that part of their suburban street was even steeper. And it is. The Dunedin City Council has the official figures to prove it