Editing 2-8-8-4 (section)

==Baltimore and Ohio==
{{Infobox locomotive
| name = B&O EM-1 2-8-8-4 Yellowstone
| image = Baltimore and Ohio Railroad (B&O) No. 7600, Class EM-1, 2-8-8-4 (Yellowstone).tif
| caption = 
| powertype = Steam
| builder = [[Baldwin Locomotive Works]]
| builddate = 1944 (20) 1945 (10)
| totalproduction = 30
| whytetype = 2-8-8-4
| uicclass = (1′D)D2′
| gauge = {{RailGauge|ussg}} [[standard gauge]]
| leadingdiameter = {{Convert|30|in|mm|0|abbr=on}}
| driverdiameter = {{Convert|64|in|mm|0|abbr=on}}
| trailingdiameter = {{Convert|38|in|mm|0|abbr=on}}
| wheelbase = {{Convert|81|ft|6.7|in|m|2|abbr=on}}
| length = Locomotive: {{Convert|83|ft|2.9|in|m|2|abbr=on}}<br />Overall: {{Convert|128|ft|8|in|m|2|abbr=on}}
| width = {{Convert|11|ft|m|3|abbr=on}}
| height = {{Convert|16|ft|m|3|abbr=on}}
| weightondrivers = {{Convert|485000|lb|kg t|abbr=on}}
| locoweight = {{Convert|627000|lb|kg t|abbr=on}}
| tenderweight = {{Convert|328000|lb|kg t|abbr=on}}
| locotenderweight = {{Convert|1010700|lb|kg t|abbr=on}}
| fueltype = [[Coal]]
| fuelcap = {{Convert|25|ST|t LT}}
| watercap = {{Convert|22000|USgal|m3|abbr=on}}
| boiler = {{Convert|100|in|m|2|abbr=on}} dia.
| boilerpressure = {{Convert|235|psi|MPa|abbr=on}}
| firearea = {{Convert|117.5|sqft|m2|abbr=on}}
| fireboxarea = {{Convert|228|by|96|in|m|2|abbr=on}} with a {{Convert|90|in|m|2|abbr=on|adj=on}} long combustion chamber
| superheatertype = Type "E"
| feedwaterheater = Worthington
| cylindercount = Four
| cylindersize = {{Convert|24|by|32|in|mm|0|abbr=on}}
| poweroutput = {{convert|6000|hp|abbr=on}}
| tractiveeffort = {{Convert|115000|lbf|kN|abbr=on}}
| factorofadhesion = 4.22
| operator = [[Baltimore and Ohio Railroad]] (B&O)
| operatorclass = EM-1
| fleetnumbers = ''7600–7629'' later ''650–679''
| lastrundate = April 19, 1960
| disposition = All thirty scrapped by 1961
}}
When the U.S. entered World War II The American railroads saw increases in traffic. The [[Baltimore and Ohio Railroad]], along with other railroads, wanted to purchase more of the [[diesel locomotive|diesel]] locomotives since they were showing improved performance over steam locomotives. But the War Production Board regulated the production of steam and diesel locomotives until the war emergency was over. So, along with producing 40 new class T-3 4-8-2 type locomotives built in-house at its Mt. Clare shops in Baltimore, Maryland, the B&O took delivery of 30 [[Baltimore and Ohio Railroad locomotives|class EM-1]] Yellowstones in 1944 and 1945, the largest number and the smallest of this type built by Baldwin as well as the most modern.

The EM-1 produced {{convert|115000|lbf|kN}} of tractive effort on {{convert|64|in|m|adj=on}} drivers with {{convert|235|psi|MPa}} steam pressure and four {{convert|24|by|32|in|m|adj=on}} cylinders.  The tender carried {{convert|22000|USgal|m3}} of water and 25 tons of coal. The engine weighed {{convert|627000|lb|t}} while the tender weighed {{convert|328000|lb|t}} for a combined {{convert|1010700|lb|t}}. Nothing bigger could operate within the tunnel clearances and track restrictions on the B&O's main line.

They were equipped with the newest technology, including the Worthington feedwater heater, superheater with front-end throttle, Cyclone front end, thermic syphons, a lateral cushioning device in the front pair of drivers on both engines and the front wheels and the trailing truck, as well as roller bearings on all axles, engine and tender, which gave them the reputation of "yard creepers", because three men could move one on a level track with the cylinder cocks open.

B&O's president, Roy B. White, after inspecting the first one delivered, said to the general superintendent of motive power and equipment, A.K. Galloway, "Well, I must say, they have everything!"

Fleet numbers 7600–7619 were built and delivered in 1944 and 7620–7629 in 1945, all by the Baldwin Locomotive Works of Philadelphia, Pennsylvania. They went to work on the Cumberland Division's rugged West End subdivision with its more than 2% grades and tight curves, where with the older 2-8-8-0 EL classes, they hauled West Virginia coal and freights. Since the EM-1s had roller bearings throughout, they also handled mail and express trains, replacing two B&O class T-3 4-8-2 Mountains. That continued until January 21, 1947, when, near Oakland, Maryland, train 29 with engine 7625 derailed with the locomotive rolling onto the engineer's side, killing the engineer. The EM-1s were then restricted to coal and freight trains until the late 1950s, when the B&O used EM-1 No. 7600 for railfan trips.{{sfn|Roberts|2001}}{{page needed|date=February 2017}}

The EM-1s also ran on the Pittsburgh Division over Sand Patch Grade near Meyersdale, Pennsylvania, with empty hoppers, iron ore or dolomite loads westbound, coal eastbound, as well as general freight in both directions. In the late 1950s, the B&O used EM-1 No. 7600 for railfan trips mostly between Cumberland, MD, and Connellsville, PA. Well-known photographer and Cumberland, MD native William P. Price captured, on still pictures and 8mm films, the EM-1s on the east side of Sand Patch pulling heavy trains with two of the B&O's 2-10-2 class S1 and S1a Big Sixes on the rear as helpers dispatched from Hyndman, PA. 
 
Near the end of steam they were all sent out to Fairmont and Wheeling, West Virginia, and Lorain, Ohio, with lake-bound coal trains as well as runs between Willard, OH and Garrett, Indiana, until the B&O started to retire them in 1957, and all of them were scrapped. Two locomotives were formerly preserved. No. 650 (7600) has earmarked for preservation by the [[B&O Railroad Museum]] in [[Baltimore]]. However, a yard master who completely misunderstood why it has to be moved, thought it was supposed to be scrapped, and the yard master ordered No. 650 to the scrapyard and broken up. As a result, he was fired by them for being a moron. No. 659 (7609) was offered to the city of [[Wheeling, West Virginia|Wheeling]], [[West Virginia]], for static display, but they denied the offer, and broken up. Thus, none of the EM-1s survive today.