What was cotton used for in the 1700s?

The cotton that was grown in the Southern colonies during the 1700s was used for the same purpose that cotton is used for today—as a material for fabric. Cotton, however, was not a major crop until the end of the century, when Eli Whitney invented and patented the cotton gin. Prior to this, the process of separating cotton fibers from its seeds was slow and labor-intensive; this limited the production capacity of the crop. That is not to say it was not grown in the South; there were a number of small but successful cotton plantations that used significant slave labor to produce and process cotton.
Cotton grown in the South was usually exported either to the Northern colonies or to Europe, particularly to England. There it would be turned into cloth that could be used to make clothing and other fabric-based products. However, because of the difficulty of processing the fibers, cotton products were expensive and usually were less popular than other fabrics, such as wool and linen. As stated before, the cotton gin changed all that. When cotton became cheaper and easier to process, it became one of the most popular raw materials for fabrics and one of North America's major cash crops. Cotton helped fuel the growth of the industrial revolution in England and the Northern United States as well as slavery in the South.
https://www.cottonmill.com/a-brief-history-of-cotton-in-america/