Erwin was a member of the Christian Democratic Union (CDU).[1] Erwin was married with Hille Erwin and had two children.
Erwin was elected Mayor of Düsseldorf in 1999.[1] He was credited with helping the city of Düsseldorf get rid of its pressing debts by selling off certain assets, such as its stake in the RWE AGutility during his tenure in office.[1] He also successfully led the effort to cut spending from Dusseldorf's budget.[1] (The city of Dusseldorf is currently populated by approximately 577,000 people and serves as headquarters to several major companies, including E.ON AG and Metro AG, which is Germany's largest retailer. [1]