The need for an organised political front to champion Sarawakian interests finally led to the formation of SUPP on 4 June 1959, with Ong Kee Hui as its founding president.

[3] With a "Sarawak for Sarawakians" ideology – SUPP's movement gained widespread support, including winning big in the local elections of November 1959, alarming the then ruling British colonial government.

[6] Party leaders vehemently protested when about 10,000 Sarawakians men, women and children were forced to resettle under curfew – surrounded by barb-wire fencing – including more than a hundred SUPP members.

[9] However, it is no stranger to major setbacks at the polls: In the 1996 Sarawak election, its then president, the late Wong Soon Kai was defeated and thereafter decided to retire from politics.

Not long after, Wong Soon Koh, who was then the deputy secretary-general, left with his faction and eventually set up a separate splinter-party with a similar-sounding name, called United People's Party (UPP).

[11] A positive turnaround was marked in the 2016 Sarawak election when SUPP, with current party president Sim Kui Hian at the helm, went on to win 7 seats out of 15 contested.

After establishing new leadership line-up and reforms including amending the party constitution to limit the tenure of the president himself, the party placed renewed focus on the pursuit of more Sarawakian autonomous power and rights within Malaysia based on the unique contexts of the federation's formation, as originally outlined in the Malaysia Agreement 1963, Inter-Governmental Committee Report, and the Report of the Cobbold Commission.