The history of the river is marked by several events: exploration, French colonization, International Wars, just to name a few. In 1604, Pierre Dugua de Mons and Samuel de Champlain explored the coast, studying the conditions and the possibilities of a settlement. They noticed that the river branched off into three directions, forming an irregular cross. An island is also located near the cross. De Mons and Champlain named both geographical landmarks, the river and the Island, Saint Croix. Beginning in 1621, the river served as a political border and controlled the amount of visiting which could take place between the English and Acadian colonies. With the advent of numerous rivalries coupled with the end of the American War of Independence and the signing of the Treaty of Paris that the Sainte Croix River becomes a truly engaging part of the U.S.-Canadian border. Nevertheless, the quarrelling continues and in 1797, the Americans claim the river as their own.

Fortunately, the resentment of the past did not affect the work of conservation and development of the Sainte Croix River undertaken by Canada and the United States. In 1982, the government of New Brunswick declared the river the “St. Croix Waterway Recreation Area” because of its potential for recreation. During the same year, the Conservation Department of Maine as well as the U.S. National Parks Service conducted a study of the river's resources, which helped to determine its category "A" classification. Because both governments saw the function of the river as that of an International Border, it received double the gratitude and attention.

It continues to be very important to preserve and protect the Sainte Croix River because it contains magnificent examples of the geologic and natural history of Canada, excellent possibilities for campsites, adventure and observation of nature. Furthermore, it offers amateur historians testimonials of the Native People's archeological and patrimonial sites, and the passage of the first Europeans in North American during the 16th and 17th centuries. In the region of Passamaquoddy Bay there are vast swamps, big lakes, rocky estuaries as well as easily flooded plains. This rich geographical area allows many sorts of rare plants to grow such as the cardinal-flower, highbush blueberry, and arrowwood, just to name a few. As for the animals and fish in the area, one can find the bald eagle, osprey, sebago salmon, smallmouth bass, and many more. It is a real paradise for the sports and fishing amateur, nature lover, and or history buff.