From what I have been able to find on the Internet, and mind you that does not mean that it is true, the sandhill get their name because of the sandy habitat that is found in the middle of Nebraska near the Platt River. Each year thousands of sandhill cranes, mostly lesser and greater subspecies, stop over at the Platt River during migration. They spend their days eating left over gains and seeds in the nearby farm fields and then roost on the sandbars of the Platt River at night. This goes on for about a month until they finally return to their migration north. Many of the greater sandhill cranes end up in Minnesota and Wisconsin, where these pictures were taken.
The sandhill crane is probably the oldest species of bird that still exists. Fossil evidence, found coincidentally in Nebraska, puts the first known sandhill crane on earth about two and a half million years ago. This is about one and a half times longer then most any other currently existing species of bird. Further more fossil records indicate that the ancestor of the sandhill crane was around about ten million years ago.