Connecticut began, as most communities at the time, as a farming economy. It rapidly developed trade and manufacturing as the farmers, and then the merchants and manufacturers themselves, became affluent enough to start buying things. Manufacturing was aided by a plenitude of resources, including water power, wood for fires and building material, and iron ore, while transportation benefited from several excellent natural harbors, and navigable rivers leading all the way to Massachusetts. As in most of New England, the residents believed that industry, in all senses of the word, not only strengthened individual moral fiber, but also served to make the colony independent and free to pursue its own religious and philosophical beliefs. While manual labor was valued, learning and study was also prized and many schools were founded, with Yale University the most significant. The development by Eli Whitney of the system of precision manufacturing of interchangeable parts and the assembly line in the late 18th century, however made Connecticut into a major center of manufacturing. This development changed "made in the United States" from a phrase connoting shoddy workmanship and expensive maintenance, into a world standard for high quality, and the entire system became known as the American system of manufacturing.