Barn construction began out of a need for:
animal shelter, grain and feed storage, and machinery protection.
A barn is an agricultural building used for storage and as a covered workplace. It may sometimes be used to house animals or store vehicles, and is often found on a farm.
On older style barns, the upper area was used to store hay and sometimes grain. This is called the mow. A large door at the top one of the ends of the barn opened up so hay could be put in the mow. The hay was hoisted into the barn by a system containing pulleys and a trolley that ran along a track attached to the top ridge of the barn.
The Barn Wood Emporium History of Barns with pictures
Enchanted Learning Barn craft activity