Northern Pacific steam locomotive 4 at Erie, Pennsylvania in 1907. Number 4 is a class V-2 built by Heisler in 1907. Photo by Heisler, J.M. Fredrickson collection. Other Subject Classes: steam locomotive in roster photo

Northern Pacific steam locomotive 4 at Erie, Pennsylvania in 1907. Number 4 is a class V-2 built by Heisler in 1907. Photo by Heisler, J.M. Fredrickson collection. Other Subject Classes: steam locomotive in roster photo

Northern Pacific steam locomotive 4 at Yacolt, Washington, circa 1910. Number 4, a Heisler, and number 7, a Lima Shay, are parked at Yacolt with other locomotives. J.M. Fredrickson collection. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 40 at Mandan, North Dakota, on July 31, 1934. Number 40, a class Y built by Schenectady in 1898, is parked at the engine terminal at Mandan. Photo by Herman Hunt, J.M. Fredrickson collection. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 40, circa 1878. Number 40 (old number series) was built by Baldwin in 1872. J.M. Fredrickson collection. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 4000 on September 18, 1916. Number 4000 is a class Z-2 built by Baldwin in 1910. Photo by Charles R. Iles, J.M. Fredrickson collection. Other Subject Classes: steam locomotive in roster photo

Northern Pacific steam locomotive 4001 at Livingston, Montana, on August 22, 1943. Number 4001 is a class Z-2 built by Baldwin in 1910. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 4002 at Bozeman, Montana, on August 22, 1943. Number 4002 is a class Z-2 built by Baldwin in 1910. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 4003 at Bozeman, Montana, on August 22, 1943. Number 4003 is a class Z-2 built by Baldwin in 1910. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 4003 at Easton, Washington, circa 1915. Number 4003 is a class Z-2 built by Baldwin in 1910. Photo by GW Pilgrim, J.M. Fredrickson collection. Other Subject Classes: steam locomotive, roster photo