Farming was by necessity the core means of survival for the first 300 years in America, augmented by fishing and hunting where possible. If you had the acreage and the head for it, you might do very well, but for most people it was subsistence farming – the only sure way to make a place for yourself and your family. A small percentage of the population were merchants, small manufacturers, and such professions as lawyers, teachers, builders, doctors, etc., and even then they may also have farmed. If you didn't have a successful farm or lucrative profession for support, you didn't run for national office as a life career, you served for a term or two and went back home to attend to making a living.
Barns were built to last using tree-sized posts and beams and the wooden pegged mortise-and-tenon construction that came from house and barn building techniques in Europe. The entire frame was erected before it was enclosed. The builders in this photo have the confidence that comes from years of construction (and they didn't have a boom crane to assist them).
Barns were a part of the landscape from coast-to-coast but only a fraction have survived; if they are no longer being used in active farming or have not been converted to other uses, they are rapidly decaying and going back into the ground from which they sprang. You will see many barns in the Timebinder collection of images – most of them survive only in photographs.