As the years went by the threshing machine was replaced by the combine. This machine was capable of moving across the field, cutting and threshing in one operation. This combined harvester and thresher was either self-propelled or was pulled by a tractor. The combine threshed the seed from the stalks of straw, collected it in a tank or sacks and then left the straw lying on the ground. The first combine was used in Michigan as early at 1837 but it did not come into general use until about 1917. They were first used on the large wheat fields. Later smaller machines were manufactured which were suitable for use on the smaller farms.
The modern combine is equipped with different types of pick-ups or heads. The grain may first be cut with a wind-rower or swather that cuts the grain and places it into long rows. The combine then comes along and "picks up" the grain and threshes it out. This method is used most often rather then straight combining because the grain has to be "just right" as far as maturity is concerned to cut with the combine. Windrow allows the farmer to cut the grain sooner and then it dries out while in the windrow.
Source: A History of Foster County 1983 Page 109