Railroad Museum of Pennsylvania, trains, history, excitement.
Skip navigation.

Read the full engrossing story of No. 3750 with additional photos, written by W. R. Rowland, an accomplished author and dedicated volunteer who helped restore it, here.

See how No. 3750 usually looks on display.

Additional publications on the K4, plus beautiful pictures, are available at the Museum's Whistle Stop Shop.

Featured Locomotive.
Click to see them all

Railroad Museum of Pennsylvania, a world class museum of railroad history in Strasburg, PA.

PRR Pacific Class No. 3750 K4
Official Steam Locomotive of Pennsylvania

K4 Specifications:
(Typical engine with Class 110P75a tender)
  • Total Length 84 ft. (with Tender)
  • Maximum Boiler Diameter 89 in.; Minimum 78.5 in.
  • Cylinder Diameter 27 x 28 in.
  • Driver Wheel Diameter. 80 in.
  • Boiler Pressure 205 lbs.
  • Grate Area 69.89 sq. ft.
  • Total Heating Surface 4041 sq. ft.
  • Total Engine Weight 320,000 lbs.
  • Tractive Force 44,460 lbs.
  • Water Capacity 11,300 gal. Coal Capacity 22 tons
  • The "s" in K4s means the boiler is superheated
  • 425 K4 locomotives were built; two survive
No. 3750, Don Wood photo. No. 3750 at Bay Head Junction, NJ in 1957,  its last year of operation. Photo by Don Wood.

Long a favorite locomotive among railfans and engineers alike, the Museum's K4s locomotive is an example of the culmination of reliable, high speed, passenger steam locomotives.  K4's pulled the fastest and most prestigious trains of the Pennsylvania Railroad for many decades, with 425 being built between 1914 and 1928. No. 3750 was built in 1920 at the PRR's Juniata shops at Altoona. They outlasted most other PRR steam passenger locomotives, with No. 3750 in steam until 1957, when the Pennsy finally halted all steam operations in favor of diesels. In their final years, they saw service on shorter lines, including the Pennsy's operations on the New York and Long Branch coast line, where many were photographed by famed photographer Don Wood, as seen above.

So successful were the K4's, that they outnumbered any other steam passenger locomotive class on any American railroad.  Over the years, a number of modifications were made to the fleet, but the basic design stayed the same. Changes included: addition of mechanical stokers on those models lacking them, newer pilots ("cow catchers"), updated peripheral appliances, relocated headlight and generator, plus some visual modernization efforts. They were featured on several of the Pennsy's famous calendar paintings by artist Grif Teller. (See art exhibits at the Museum, here.)

When pulling long or heavy trains, it was common for two K4's to be coupled together to provide the needed power. Since each engine had a separate crew of engineer and fireman, detailed operating rules were in place to assure that the two engines worked in harmony.

Harding's funeral train.No. 3750 was a typical workhorse, with only two unusual events in its long and productive life.

One was that early in its life, it pulled President Harding's funeral train, seen here in 1923 draped in black bunting, preparing to depart Washington for Baltimore.

The second was more unusual. After its retirement from active service in 1957, it remained in storage, first at West Philadelphia enginehouse, then at Northumberland, along with other historic equipment that was destined to become the core of the Museum's holdings. However, the Pennsylvania Railroad, apparently chagrined that the first K4 ever built, No. 1737, had been scrapped because it was worn out, decided to "undo" history by placing No. 1737's number plates onto No. 3750. Thus, No. 3750 in its masquerade avoided being sent to the scrapper's torch along with hundreds of other K4 locomotives.

Thus, it arrived at the Museum along with other historic equipment in 1968 as a "ringer" for No. 1737. This was rectified when the newly formed Friends of the Railroad Museum performed the first of several laborious restorations of this beloved locomotive in the 1980s. At one point, there were discussions of repairing it to be able to steam, but this was not undertaken. Subsequently, the true No. 3750 plates were obtained, and this wonderful locomotive is now secure for future generations to admire.

Interestingly, the tender still bears the deceptive 1737 identification, yet even changing that to 3750 would not be correct. For although locomotives and tenders were generally built as a pair for life, they were sometimes switched around to meet operating requirements, and this tender was built by Baldwin Locomotive Works in 1926 for M1 Mountain class locomotive No. 6904.

K4s locomotives 3750 and 1361 were designated "The Official Steam Locomotives of the Commonwealth of Pennsylvania" by the Pennsylvania State Legislature and Governor Robert Casey in 1987.

3750 Number Plate.

1932 Pennsylvania Railroad calendar painting by Grif Teller.


Frequently asked questions about the K4:

What is its wheel arrangement? K4 locomotives are of the Pacific class, with a wheel arrangement of 4-6-2, meaning that their lead truck has four wheels, with six driving wheels, and two wheels on the trailing truck.

Where is No. 3750? We move our locomotives around from time to time. It is often seen heading up a 1950's vintage passenger train inside the exhibit hall. It is currently undergoing some additional restoration, and may not be on display there.

Where is the other surviving K4? No. 1361 was for many years on static display at Horseshoe Curve in Altoona. It was restored to operating condition for excursion use, but encountered extensive problems of age and wear, requiring major rebuilding; it is under ownership of the Railroaders Memorial Museum at Altoona.

Could 3750 operate? A common question about our locomotives. Yes, with the expenditure of hundreds of thousands of dollars, it could be made operable again. But the infrastructure that once supported the vast steam power system no longer exists, and maintenance would be difficult. And why inflict further wear upon this precious survivor of America's Golden Age of Railroading? Our goal is to preserve history.


Read More About No. 3750


To page top.
Administered by the Pennsylvania Historical and Museum Commission
Assisted by the Friends of the Railroad Museum of Pennsylvania
Signalling history, excitement, trains.
PHMC Logo.
Privacy and Legal Notices     Contact Us   Copyright © Friends of the Railroad Museum of Pennsylvania     Site Design by Jimquest Communications

Find us on Facebook.      Instagram