About this time a distinguished French geographer, M. Nicollet, was sent to this country by France to explore the sources of the Mississippi, "in the interests of geography." The United States were also interested in the geography of the almost unknown Northwest. M. Nicollet was appointed to make explorations for the United States, and Frémont was honored with the position of principal assistant. It was high time that something should be done in the interests of a geography made up largely from travellers' tales. That there was a great river, the Buena Ventura, running from the base of the Rocky Mountains to the Bay of San Francisco, nobody doubted, for there it was upon the map. The exploration of M. Nicollet, assisted by Frémont, awakened great interest. They were absent two years; their field, the territory between the Missouri and the upper rivers, as far north as the British line. Their report was awaited with impatience. Frémont came home to find that he had been appointed second lieutenant of the United States Topographical Engineers. As a scientific explorer his fame was established. The year following his return he spent in Washington with M. Nicollet, preparing his report for publication. Among those most deeply interested was Senator Benton, of Missouri, "Tom Benton," as he was popularly called, and "Old Bullion." Benton's hobby was the opening of a road for immigrants to the Pacific coast, as a necessary step to the acquisition of the territory held by Mexico--the California of to-day. Senator Benton's interest in the report of the young engineer, then about twenty-seven years of age, was surpassed by the young engineer's interest in the senator's daughter, Jessie, then only fifteen, an interest which ended in a betrothal contrary to the wishes of older heads, owing to Miss Benton's youth and young Frémont's connection with the army. The young engineer received an unexpected and unwelcome order, sending him to the wild frontier of Iowa at once, where the Sacs and Foxes, it was thought by Senator Benton (who had a hand in his exile), might be made to help postpone the marriage, at least. But banishment and red-skins were of no avail in breaking the engagement. Frémont performed his duty to the letter, returned to Washington, and married Miss Benton, October 19, 1841--a "runaway match" which happily brought life-long happiness to both parties--Mrs. Frémont becoming the connecting link, to use her own words, between her father's "fixed idea of the importance of the speedy acquisition of the Pacific coast, and its actualization through the man best fitted to be the pioneer of the undertaking." Less than a year after his marriage, in the summer of 1842, Frémont was sent by the War Department on the _first_ of the _five_ expeditions which gave him the name of Pathfinder. The Mexican War was ripening fast. England had at that time financial claims upon Mexico, and Mexico was bankrupt.