The Pennsylvania barn is a distinctive barn design that gained popularity in the United States between 1790 and 1900. It is easily recognizable due to its prominent forebay, which refers to an area where one or more walls extend beyond the foundation. Most Pennsylvania barns feature gable roofs and were constructed into the sides of hills, enabling convenient access to both the basement and ground level of the barn.

Historian Robert Ensminger has classified Pennsylvania barns into three main types: standard, Sweitzer, and extended Pennsylvania barns. The standard Pennsylvania barn is the most common and widely found variation, while the Sweitzer barn is considered the original Pennsylvania barn. The extended Pennsylvania barn is a larger version of the standard design.

One of the reasons Pennsylvania barns became popular is their versatility, as they could be tailored to meet the specific needs of individual farmers. These barns varied in size, ranging from 20 feet long to well over 100 feet. They could house different types of livestock such as horses, cows, sheep, or pigs. The lower level of the barn was utilized for animal shelter, while the upper level served for processing and storing hay and grain.

Pennsylvania barns have stood the test of time, and many of these historic structures can still be found throughout America today. They represent an important part of the agricultural heritage and serve as a testament to the ingenuity and adaptability of early American farmers.