SP&S 4-6-6-4 steam locomotive Number 900, Class Z-6, at the Northern Pacific roundhouse at Parkwater in Spokane, Washington.

SP&S 4-6-6-4 steam locomotive Number 900, Class Z-6, charges out of the Great Northern Hillyard yard in Spokane, Washington.

SP&S 4-6-6-4 steam locomotive Number 900, Class Z-6, at the Northern Pacific roundhouse at Parkwater in Spokane, Washington.

SP&S 4-6-6-4 steam locomotive Number 900, Class Z-6, at the shops at Vancouver, Washington in 1938.

SP&S 4-6-6-4 steam locomotive Number 900, Class Z-6, on the turntable at Vancouver, Washington.

Color photo of SP&S 4-6-6-4 steam locomotive Number 900, Class Z-6, at Vancouver, Washington.

SP&S 4-6-6-4 steam locomotive Number 901, Class Z-6, works freight train Number 276 by Pasco, Washington on March 21, 1939.

SP&S 4-6-6-4 steam locomotive Number 901, Class Z-6, at the Northern Pacific servicing facilities at Pasco, Washington on May 9, 1938.

SP&S 4-6-6-4 steam locomotive Number 901, Class Z-6, at the Great Northern yard at Hillyard in Spokane, Washington in July 1947.

SP&S 4-6-6-4 steam locomotive Number 901, Class Z-6, at the Great Northern yard at Hillyard in Spokane, Washington in July 1947.