[1] After independence from the United Kingdom, Tanganyika adopted a first constitution based on the Westminster Model (with the exclusion of the Bill of Rights).

This defined a Governor General who represented the Queen of Tanganyika, Elizabeth II, to be the formal head of state.

In 1962, the Tanzanian Parliament (made solely of nominees from the Tanganyika African National Union party) formed itself into a constituent assembly and drastically revised the 1961 constitution, most notably with the establishment of a strongly presidential system.

The new President of Tanzania was granted the prerogatives of both former roles, Governor General and First Minister, serving as the head of state as well as commander in chief of the armed forces.

The most notable feature of the Acts of Union was the establishment of the double government structure that is also part of Tanzania's current constitution.

For example, an amendment in 1975 established that all the government institutions, including the Parliament, were subordinate to the party's executive committee.

In the early 1990s, President of the Union Ali Hassan Mwinyi launched a program of liberal reforms.

The Ninth Amendment reorganized presidential elections and introduced the possibility of impeachment by the Parliament; further, it separated the functions of President and Prime Minister.