From this frontier commerce, North Dakota industry grew. In 1909, a century after the fur trade began, the State produced goods valued at $19,150,000; and in 1935 manufactures were valued at $40,076,326, with 325 establishments each doing an annual business of $5,000 or more, and collectively employing 3,306 workers. Although these figures are small in comparison with those of essentially industrial States, they are large in view of the youthfulness of North Dakota and its distinctly agricultural economy. The fur trade prospered until the Indian insurrections of 1863-64. Then trapping became a perilous occupation, and traders and trappers returned East. Eastward, too, went most of the settlers who had come to farm. The only ones to remain were Charles Cavileer and his little colony at Pembina, who staunchly continued to cultivate their level farms in the face of Indian dangers. With the exception of a few brave adventurers, they had the entire area virtually to themselves, until the extension of the Northern Pacific lines into the Red River Valley in 1871 promoted a period of homesteading. Then, for the first time, agriculture took its place as the leading occupation of this area. Many of the industries which were important during the development of the State are no longer in existence. Because lumber was an expensive commodity to import, sawmills were established at Grand Forks and Fargo in the 1870's; and because the North Dakota side of the Red River could not furnish a large enough supply for the mills, logs were floated down from the Minnesota woods. Lumberjacking meant cash and wages, and many homesteaders left their families in possession of their claims while they went to Minnesota to earn money for seed and machinery and for building permanent homes on their farms. As traffic on the Red River increased, construction of steamers became an important industry for which North Dakota mills supplied much of the lumber. On the prairies west of the Red River Valley, the homesteaders could not engage in logging and lumbering to earn money for improving their farms; but, resourcefully, they found another way to get funds. Buffalo bones were scattered abundantly upon the land from Devils Lake westward, and cash prices of eight to ten dollars a carload were paid by sugar manufacturers who used the bones in a refining process. Many homes were built and much machinery purchased with the income derived from gathering and selling this material. Gradually, however, these pioneer occupations died out. The more efficient railway supplanted the river steamers. The supply of buffalo bones was soon exhausted. New occupations, allied with the expanding agriculture of the region, grew into importance.