That type of tender was known on the Santa Fe as a whaleback. Slopeback tenders were typically used with switch engines not road power - though, as always, there were exceptions. The biggest problems Santa Fe had with the 2-10-10-2s were with their jointed boilers.

That slopeback tender behind the first loco was uniquely used on the Santa Fe, and was not original equipment on that particular engine. It came originally attached to one of the 2-10-10-2 mallets used to push trains over Cajon Pass. Built early in the century, they were the world's largest locomotives in their day, yet proved so impractical and labor intensive that they were short lived, like most behemoth locomotives produced in that era. They were scrapped in the 1930's, and MAY have been (I don't have my Santa Fe books handy, so don't quote me on it) converted into two 2-10-0 types.

Engines died, but tenders, especially practical designs like the slopeback, lived on until the very end of steam.

There's a group up at the University of Minnesota working with some 501c3 organization refitting a Baldwin to run on Biomass. They think they can get better emissions, efficiency, and power than diesel once they get it right. Even got themselves a website: http://www.csrail.org/.

It would be awfully neat if we could see these kinds of things again!

The Santa Fe steam locomotive 1691 in the photo, is one of the earliest examples of a locomotive type which was named after the railroad. They descend from the 2-10-0 "Decapod" type, to which the Santa Fe added a one axle "trailing truck" under the cab in 1903, for better tracking on the steep and curvy Raton Pass grade in Colorado and New Mexico.
This begot one of the most popular wheel arrangements in America for heavy freight service.