[1] The Caledonian Union was born as a cross-community (multi-ethnic) autonomist party led by Maurice Lenormand, who was the island's sole representative in the French National Assembly.

"[2] The party's first significant success was on February 8, 1953 with the election of 15 members of the Caledonian Union to the 25 seats General Council.

[3][4] However, the UC opposed the arrival of Gaullist centralism in France, which undid most of the autonomist reforms of the French Fourth Republic (the Defferre laws).

The UC grew more and more radical, and started flirting with independence, which eventually led to an outflow of the Caldoche members of the Caledonian Union to new loyalist parties, such as the Rally for Caledonia in the Republic.

In 1977 in Bourail, the UC adopted a nationalist platform that changed the party's ideology from autonomism to full independence from France.