When the Union of South Africa was formed in 1910, the electoral qualifications in use in each pre-existing colony were kept in place.

The first challenge to the Cape Qualified Franchise came with the Women's Enfranchisement Act, 1930 and the Franchise Laws Amendment Act, 1931, which extended the vote to women and removed property qualifications for the white population only – non-white voters remained subject to the earlier restrictions.

In 1936, the Representation of Natives Act removed all black voters from the common electoral roll and introduced three “Native Representative Members”, white MPs elected by the black voters of the province and meant to represent their interests in particular.

In 1924, the constituency was briefly abolished, its territory divided between Cape Town-Hanover Street and Salt River, but in 1929 it returned.

In its second iteration, Woodstock became a safe seat for the United Party, which faced only Communist opposition in 1943 and an independent candidate in 1948.