It covered much of the southern half of the North Island until November 1858, when Hawke's Bay Province split off, taking about a third of its area.

Wellington Province originally covered much of the southern half of the North Island.

Its northern boundary was drawn arbitrarily across most of the middle of the island at latitude 39° south to the east coast, just including the entirety of Hawke Bay.

According to Statistics New Zealand figures at the 2001 census 626,000 people lived within the provincial boundaries.

Wellington Anniversary Day is the Monday that falls closest to 22 January and is observed as a public holiday within the old provincial boundaries.