Initially Carver was unable to find a sponsor for his proposed explorations but in 1766, Robert Rogers contracted Carver to lead an expedition to find a western water route to the Pacific Ocean, the Northwest Passage. There was a great incentive to discover this route. The king and Parliament had promised a vast prize in gold for any such discovery. The eastern route to the Pacific was around the Cape of Good Hope. That route was both lengthy and contested by competing European powers.
In 1766-67 he explored parts of present-day Wisconsin, Minnesota, and Iowa, mainly along the upper Mississippi River. When he returned east, however, his efforts were not recognized. He sailed to England in 1769, seeking recompense, and remained there for the rest of his life. In 1778 he published a book on his travels, which became very successful. He died in 1780.

Following his death, some of his heirs claimed to that he had obtained a land grant from two Sioux chiefs for a large area of eastern Wisconsin during his voyage; however, the grant was legally invalid and may have been a later fraud.
Carver, Minnesota, Carver County, Minnesota and Jonathan Association in Chaska, Minnesota were named in honor of Jonathan Carver for his exploration and mapping of the region.