A rod is 16.5 feet long. When farmers first fenced off the American prairie, they placed posts a rod apart. This was a good distance to hold up a wired fence, and it also made estimating the number of posts a farmer needed easier.
A quarter mile is exactly 80 rods long, and so farmers could use this measurement to determine how many fence posts they needed. When homesteaders settled in Nebraska, each one received one quarter section, or 160 acres. Spacing posts a rod apart along this perimeter meant that the space in between fence posts represented an acre when measured all the way across the quarter section. Even today, it is common to space fence posts a rod apart.