The early history of the Cajuns is a tale of endurance against outside forces bent on their destruction. In the 17th century, the first European settlers left western France and sailed for the new world. Their destination was Cadie, or Acadia, a region of New France that is now called Nova Scotia. There, they and their descendants lived until 1755, when they were forced to leave by the British authorities. Many Acadians were deported to English colonies in what is now the southern U.S. More wandered to the West Indies and elsewhere. Most of them eventually ended up as subsistence farmers in South Louisiana, where there was already a French population, and where the Spanish government welcomed Catholic immigrants.

In Louisiana, they reconstructed their culture and made modifications to suit their new environment. They had contact with new groups, principally Native Americans and free people of colour. This environment allowed Acadians, who in their rough and ready French called themselves "Cadiens" or "Cajuns", to combine elements of French, Celtic, Spanish, Native American and African music into a new and unique musical genre: Cajun music. This genre had almost two centuries to develop, mature and mellow before the first entrepreneurs and collectors arrived on the scene to make records. The history of commercially recorded Cajun music, which goes back only to the late 1920s, can be read in part as the story of a long sibling rivalry. Big brother fiddle was with the Acadians in Canada, and its music was the base of the Cajun sound. Chromatic and fretless, it could easily handle all the subtleties of Cajun music, and was in many ways the primary instrument. Little brother accordion was newer on the scene and more limited in ability. Only seven different notes were available to the Cajun accordion, a single diatonic key. But what it lacked in subtlety, the accordion made up for in volume and sheer indestructibility. Four banks of reeds provided a huge sound that could be heard in a noisy house party, and its sturdy, boxy construction proved much less fragile than the fiddle's delicate, exposed fingerboard, strings and bridge.

During much of Cajun music's recorded history, the two brothers have worked together beautifully and without complaint, but sometimes, as a result of broader social and historical patterns, one or the other has taken centre stage. For example, the accordion was basically the main instrument of recorded Cajun music for a few years in the 20s and early 30s, since it made as much sound as the big bands that most record companies were used to recording, and since the accordion was still riding a wave of popularity based on its novelty. But, during the 1930s, Louisiana underwent social upheaval that brought the fiddle to the fore. The advent of amplification made the accordion's natural loudness less of an advantage, and the German factories where accordions were made shifted their energies to produce Hitler's war machines, so accordions became scarce. At the same time, the discovery of oil brought industrial jobs and newcomers to the state, and new roads and bridges made South Louisiana more accessible to outsiders and the outside more accessible to South Louisiana. The result was an Americanization process in which string bands, western swing and western country music were emulated by Cajuns. The fiddle simply got along better with the English-speaking neighbours. Along with new arrivals like the pedal steel, the fiddle began to dominate the music scene as Cajun string bands were born.