Blair's school instruction, obtained during a few brief months in the winters, ceased when he was eleven years old, and he went to work in a country store.
At eighteen Blair was his own master and owner of a store. At twenty-seven he had a chain of five general stores in the northern part of New Jersey and ran four flouring-mills. In 1833 he became interested with Col. George W. Scranton and Seldon T. Scranton in the mines at Oxford Furnace. Success in this enterprise led in 1846 to his participation in the founding of the Lackawanna Coal & Iron Company. Mining led to railroad promotion, and it was in this enterprise that he amassed the greater part of his fortune and reputation. In 1852 the Delaware, Lackawanna & Western Railroad, so named at Blair's suggestion, was organized. He served as a director from the organization of the road until his death.
In 1860, when attending the convention at Chicago, Illinois, which nominated Abraham Lincoln, Blair's attention was attracted to the great possibilities of Western development through the extension of railroads. He joined with Oakes Ames and others in getting the charter of the Union Pacific Railroad, and personally built the first one hundred miles west from Omaha, having been responsible for the adoption of that route. His operations in the West extended in succeeding years to Iowa, Wisconsin, Kansas, Nebraska, Dakota, Missouri, and Texas. He laid out sites for more than eighty towns, and owned lands equal to half the area of his native state.
Blair continued to reside in New Jersey in his beloved Blairstown, his enormous enterprises being directed from this inaccessible little village. One of the institutions which claimed his special favor and attention was the Blair Presbyterian Academy at Blairstown. Blair Hall at Princeton University, of which institution he was made a trustee in 1886, is another monument to his liberality. Grinnell and Lafayette Colleges were also special recipients of his benevolences. The value of his estate was roughly estimated at the time of his death at $70, 000, 000 and he was said to have given away over $5, 000, 000.
Blair was a most liberal benefactor of the Presbyterian Church, of which he was a life-long member. In the eighty towns in the West, whose sites he was instrumental in selecting, he helped erect, by gifts of land and money, more than one hundred churches.
Blair was always keenly interested in politics, state and national. He attended every national convention of the Republican party from its founding till 1892. In 1868 he was the unanimous choice of the New Jersey state Republican convention for governor, but lost the election to Gov. Randolph. The campaign cost Blair over $90, 000 personally.
Blair was a man of unusual energy and possessed a remarkable physique. He told friends that it had been his custom to travel about 40, 000 miles a year and that he reduced this to 20, 000 only when he reached the age of eighty-five. When ninety-two years old, he would often be at his desk at 5:30 a. m. , and business would then claim his attention during the greater part of the day. His habits were always simple, and his acquisition of millions made little change in his mode of living.
Blair married, September 20, 1828, Ann Locke of Frelinghuysen, New Jersey, granddaughter of a Revolutionary captain.