In the late nineteenth century, as cities like Boston and New York grew more congested, the streets became clogged with plodding, horse-drawn carts. When the great blizzard of 1888 crippled the entire northeast, a solution had to be found. Two brothers from one of the nation's great families-Henry Melville Whitney of Boston and William Collins Whitney of New York-pursued the dream of his city digging America's first subway, and the great race was...