The animal was an adult male in its 40s, and researchers excavated its skull, tusks, vertebrae and other bones, says the Detroit Free Press.
The discovery was an accident. The farmers were digging a drainage ditch when they hit what they first thought were large pieces of wood.
University of Michigan researchers say there is evidence the mammoth lived 11,700-15,000 years ago. It may have been killed by humans and left in a pond for storage.
Dr Dan Fisher, director of the university`s Museum of Paleontology, told reporters that the bones could help scientists determine when the first humans arrived in the area.
The landowner could only give researchers a single day to unearth the bones because of a tight harvest schedule, so excavators worked feverishly until sundown on Thursday.
Only 30 mammoths have been discovered in Michigan, and it is extremely rare to find a skeleton as complete as this one, says Fisher.
