Willemstad on Curaçao was the actual capital of the Netherlands Antilles during the Dutch colonial period. For this reason the town could boast not only the government buildings, but many other representative premises as well, among which several military and state buildings. Business offices, premises for ship-owners and banks and administrative offices, and such were built. These functions and institutions continued to exist even after the colonial status was officially abolished in 1954.

The Charter for the Kingdom of the Netherlands that was drawn up at that time (and later modified several times) stipulates that the Kingdom comprises Aruba, the Netherlands Antilles and the Netherlands. Each of these has its own government, but they all have one Head of State [the King or Queen], one Minister for Foreign Affairs and one army. The countries are autonomous with respect to internal affairs, but constitute one Kingdom vis-à-vis foreign countries. Willemstad is the capital of the Netherlands Antilles. However, the Charter is currently being revised to include Curaçao and St. Maarten as separate countries within the Kingdom. In a few years time, therefore, Willemstad will no longer be the capital of the Netherlands Antilles but only of Curaçao itself.

Important to the economy and development of Curaçao and Willemstad was the establishment of a Shell oil refinery during World War I. Shell disposed of its refinery in 1984, but the installations are still running.