The 4-4-0 American can be given overwhelming credit, more than any other
steam locomotive design before or since its development, for helping the
United States flourish beginning in the latter half of the 19th century.
After their debut and minor refinements the 4-4-0 wheel arrangement quickly
proved its superior ability over all other types of its day and by the 1870s
well over three-quarters of all steam locomotives operating in the country at
that time were American Types! While the railroads themselves built our great
nation into what it has become today, their initial workhorse in achieving
that task was certainly the 4-4-0.