The Federal Party existed from 1953 at a Federal level, as well as territorially in Northern Rhodesia (Zambia) and Nyasaland (Malawi). In Southern Rhodesia (Zimbabwe), a territorial Federal Party organisation existed, but not Federal Party participation in territorial politics. To complete its territorial coverage, a merger was arranged with the (Southern Rhodesian (Zimbabwean)) United Rhodesia Party (URP) in 1957/1958 to create the United Federal Party (UFP). This development became embroiled in the cabinet crisis of R.S.G. Todd's United Rhodesia Party government in Southern Rhodesia (Zimbabwe) (see MSS. Welensky Papers 470/1-2), out of which, somewhat uncertainly, a new or revived United Rhodesia Party arose (see MSS. Welensky Papers 516/4-517/1).

In early 1963, with the demise of the Federation (Zimbabwe, Zambia, and Malawi) all but certain, the three territorial wings of the United Federal Party split off as the National Progress Party (Northern Rhodesia (Zambia)), the Nyasaland Constitutional Party, and the Rhodesia National Party (Southern Rhodesia (Zimbabwe)). The Federal husk resumed the title of the Federal Party.

Immediately after the demise of the Federation, Welensky established himself in an office in Salisbury (Harare) in the Old Lonrho Building, which had been vacated by the defunct Federal Party. His daughter, Joan (Mrs Denis Bridge), who had previously worked as secretary to the General Secretary of the (United) Federal Party, became his secretary and office manager. At this point, further United Federal Party archives seem to have attached themselves to those papers that Welensky had received over the years as party leader. The United Federal Party Central Office files are listed at MSS. Welensky Papers 523/1-532/10. Material of uncertain provenance has been included in sections appropriate to its having formed part of Welensky's papers.

In the current section, the Federal Party and United Federal Party are treated separately, as far as possible. Certain bodies, such as the Caucus in the Federal Assembly, carry through from the one party to the other. Federal committees and activities are catalogued before territorial ones for each party. Insofar as the files are Welensky's own set, a degree of incompleteness may be anticipated in respect of party committees he did not attend or of which he was not a member (and of whose proceedings he received, subject to any deficiencies of party organisation, a copy 'for information').

Certain material carries over to the United Federal Party, in particular that relating to publicity and publications at MSS. Welensky Papers 491/1.