The year 1850 saw the great compromise upon slavery in the Southwest, a compromise made necessary by the appearance on the Pacific of a new America. The "call of the West and the lust for gold" had done their work in creating a new centre of life beyond the quondam desert.
The census of 1850 revealed something of the nature of this population. Probably 125,000 whites, though it was difficult to count them and impossible to secure absolute accuracy, were found in Oregon and California. Nine-tenths of these were in the latter colony. More than 11,000 were found in the settlements around Great Salt Lake. Not many more than 3000 Americans were scattered among the Mexican population along the Rio Grande. The great trails had seen most of these home-seekers marching westward over the desert and across the Indian frontier which in the blindness of statecraft had been completed for all time in 1840.
The long line separating the Indian and agricultural frontiers was in 1850 but little farther west than the point which it had reached by 1820. Then it had arrived at the bend of the Missouri, where it remained for thirty years. Its flanks had swung out during this generation, including Arkansas on the south and Iowa, Minnesota, and Wisconsin on the north, so that now at the close of the Mexican War the line was nearly a true meridian crossing the Missouri at its bend. West of this spot it had been kept from going by the tradition of the desert and the pressure of the Indian tribes. The country behind had filled up with population, Oregon and California had appeared across the desert, but the barrier had not been pushed away.
Through the great trails which penetrated the desert accurate knowledge of the Far West had begun to come. By 1850 the tradition which Pike and Long had helped to found had well-nigh disappeared, and covetous eyes had been cast upon the Indian lands across the border,--lands from which the tribes were never to be removed without their consent, and which were never to be included in any organized territory or state. Most of the traffic over the trails and through this country had been in defiance of treaty obligations. Some of the tribes had granted rights of transit, but such privileges as were needed and used by the Oregon, and California, and Utah hordes were far in excess of these. Most of the emigrants were technically trespassers upon Indian lands as well as violators of treaty provisions. Trouble with the Indians had begun early in the migrations.