Born in Mariahilf, Vienna's 6th district, in 1900, Marek attended a business school before participating in the latter stages of the First World War in 1918.

After the war, during the period of Red Vienna, he became involved in the Social Democratic Party (SPÖ).

After the victory of the Austrofascists in the Austrian Civil War, the SPÖ was banned, and Marek was imprisoned.

After Mayor Franz Jonas was elected President of Austria in 1965, Marek replaced him on 10 June 1965.

[2] During Marek's mayorship, the city planned and began building the U-Bahn, the Spittelau incineration plant, and the fourth Danube bridge, the Praterbrücke.