Kirkwood had come to the United States in 1832 with letters to McNeill, who arranged work for him on the Norwich Worcester Railroad. He served on the Boston & Providence Railroad, and in 1835 became Assistant Engineer of the Stonington Railroad. In that same year he surveyed the route for the Long Island Rail Road, which was opened from the foot of Atlantic street to Hicksville in 1837. He had charge of the construction of that road until operations were stopped by the panic of 1837.