Close upon the heels of the overland migrations came an organized traffic to supply their needs. Oregon, Salt Lake, California, and all the later gold fields, drew population away from the old Missouri border, scattered it in little groups over the face of the desert, and left it there crying for sustenance. Many of the new colonies were not self-supporting for a decade or more; few of them were independent within a year or two. In all there was a strong demand for necessities and luxuries which must be hauled from the states to the new market by the routes which the pioneers themselves had travelled. Greater than their need for material supplies was that for intellectual stimulus. Letters, newspapers, and the regular carriage of the mails were constantly demanded of the express companies and the post-office department. To meet this pressure there was organized in the fifties a great system of wagon traffic. In the years from 1858 to 1869 it reached its mighty culmination; while its possibilities of speed, order, and convenience had only just come to be realized when the continental railways brought this agency of transportation to an end. The individual emigrant who had gathered together his family, his flocks, and his household goods, who had cut away from the life at home and staked everything on his new venture, was the unit in the great migrations. There was no regular provision for going unless one could form his own self-contained and self-supporting party. Various bands grouped easily into larger bodies for common defence, but the characteristic feature of the emigration was private initiative. The home-seekers had no power in themselves to maintain communication with the old country, yet they had no disposition to be forgotten or to forget. Professional freighting companies and carriers of mails appeared just as soon as the traffic promised a profit. A water mail to California had been arranged even before the gold discovery lent a new interest to the Pacific Coast. From New York to the Isthmus, and thence to San Francisco, the mails were to be carried by boats of the Pacific Mail Steamship Company, which sent the nucleus of its fleet around Cape Horn to Pacific waters in 1848. The arrival of the first mail in San Francisco in February, 1849, commenced the regular public communication between the United States and the new colonies. For the places lying away from the coast, mails were hauled under contract as early as 1849. Oregon, Utah, New Mexico, and California were given a measure of irregular and unsatisfactory service.