Traveling from East to West required the pioneers to travel with many things- clothing, food supplies, tools and some furniture- This required large wagons that would hold a lot of weight- sometimes several tons. Covered wagons were a way to transport their loads and ptrotect it from the elements.
The first covered wagon was designed in Pennsylvania and was called a Conestoga wagon. It's ends were angled and the floor sloped to the middle to prevent barrels from rolling out when going uphill or climbing mountains. Conestoga wagons were used the most by pioners traveling the Santa Fe trail.
Pioneers taveling the Oregon Trail found that these wagons were too heavy for their needs- many times killing the oxen that were trying to pull them before their destination was reached.
Thus a smaller wagon about half the size of the Conestoga was invented. These smaller wagons were called " Prairie Scooners".