Narrow Gauge Locomotive Builders.

Baldwin Locomotive Works.
1832 - 1952. Philladelphia, Pennsylvania.

Brooks Locomotive Works.
1869 - 1901. Dunkirk, New York.

Dawson & Bailey / National Locomotive Works.
1871 - 1878. Connellsville, Pennsylvania.

H. K. Porter.
1866 - 1950. Pittsburgh, Pennsylvania.

Grant Locomotive Works.

Mason Machine Works.
1845 - 1944. Taunton, Massachusetts.

Articles:

Locomotive Manufacturer Charts
From "American Narrow Gauge Railroads" by George Hilton.

Sand Dome Designs
By David Fletcher.
Illustration comparing sand dome designs and their relation to classical architecture used by American locomotive builders.