The Union Pacific has long been one of America's favorite railroads and is a popular subject for model railroading. The last types of UP steam power, the 4-12-2 Union Pacific types, 4-6-6-4 Challengers, 4-8-4 Northerns and 4-8-8-4 Big Boys were successful and long serving locomotives and among the largest and most powerful steam locomotives ever built. The many years of excursion service by 844 and 3985 have made models of those locomotives at home on steam era and contemporary model railroads alike. The movement of UP Big Boy 4014 from static display in California back to Cheyenne for restoration to service has created renewed interest in the Big Boys and the trains that they pulled. Since every real freight train needs a caboose the topic of what UP caboose is appropriate to go with UP 4014 or other locomotives has been a frequent topic of conversation in recent months. This thread is intended to provide a reference source for prototypical O scale UP cupola cabooses.
Wood Cupola Cabooses
The earliest UP cabooses were of wood construction and built to a variety of designs. When the UP came under Harriman control in the first decade of the 20th century the new management adopted standard designs for use on the UP as well as the other railroads in the Harriman empire. Older UP cabooses were then classified as Non Common Standard or NCS. New cabooses were built to the common standard and classified as CA. The CA design was externally similar to some of the NCS cabooses. NCS cabooses had been built with wood frames as was common at the time. The CA cabooses had steel reinforced wood underframes for greater strength. Starting in 1918 new UP cabooses were built using the familiar superstructure of the CA but had all steel underframes and were assigned to class CA-1. UP CA-1 cabooses served into the 1960s.
Steel Cupola Cabooses
There was a halt to new caboose construction on the UP that lasted form the mid 1920s into the 40s . While a CA-2 class was considered none were constructed. The next UP cabooses were built to a new all steel design in 1942 by Mt Vernon Car Company. Classified as the the CA-3, they set the pattern for UP caboose design through the CA-10 of the mid 70s. While later versions had detail differences they all shared the same basic dimensions and internal arrangements.
As delivered the CA-3s featured a running board across the top of the cupola. The running boards were soon deemed unnecessary. They were removed from the CA-3s and not repeated on any subsequent class of UP cupola caboose. The CA-4 class followed in 1944. All of the CA-3s and CA-4s were delivered with a very old style wood beam truck. The UP liked the riding qualities of the composite construction and specified them for the CA-3 and CA-4 cabooses.
Today's O scale Models
We have two excellent models available in O scale today to represent UP wood and steel cupola cabooses. The MTH CA-1 is an excellent model and can credibly stand in for earlier CA and some NCS cabooses. The Lionel CA-3/CA-4 caboose is also a fine model of the first UP steel cabooses. This list of recently produced models is in approximate chronological order for the prototypes. The UP changed lettering style on their cabooses in 1939 and switched from mineral red to Armor Yellow starting in 1947. The UP renumbered cabooses from four to five digit numbers starting in 1959. The CA-3 and CA-4s received their new numbers by 1960 and the wooden cabooses followed more slowly.
The MTH 20-91292 appeared in the 2009 Volume 2 catalog. It depicts CA-1s built by Mt. Vernon in 1923 and carries the pre-1939 lettering style.
The MTH 20-91291 appeared in the same catalog and and depicts CA-1s built by Mt. Vernon for UP subsidiary Los Angeles & Salt Lake. It features the post-1939 lettering style.
The MTH 20-91161 and 20-91256 appeared in the 2005 Volume 1 and 2008 Volume 1 catalogs respectively. They both depict NCS cabooses built in 1901 by American Car and Foundry and have post 1939 style lettering.
The MTH 20-91557 appeared in the 2015 Volume II catalog. They have post-1939 style lettering.
The Lionel 6-27633 was featured in the 2010 Volume 1 catalog and depicts the last CA-3 as delivered with its cupola top running board.
The Lionel 6-17690 debuted in the 2006 Volume 2 catalog and is an accurate representation of a CA-4 as delivered in 1944.
The Lionel 6-27667 appeared in the 2011 volume 2 catalog. It depicts a CA-4 that wore experimental high visibility black and white stripes on its ends in 1947 and 48.
The MTH 20-91255 was featured in the 2008 Volume 1 catalog. The two numbers offered depict a CA and a CA-1 in Armor Yellow.
The MTH 20-91290s from the 2009 volume 2 catalog represent CA-1s delivered to the Oregon Short Line from Standard Car in 1914.
The MTH 20-91317s appeared in the 2010 volume 2 catalog and represent the last CA-1s built by the UP. They came from the OWR&Ns Albina Shops in 1924.
The MTH 20-91447 appeared in the 2015 Volume I catalog.
Lionel's 6-81840 is in the 2014 Signature catalog a depicts a CA-4 as repainted into the Armor Yellow scheme starting in 1947.
The 20-91140 was the first model of a UP CA-1 offereed by MTH. It was featured in the 2004 Volume 2 catalog and has Armor Yellow ends with white side and a safety slogan. This paint scheme was applied to some UP cabooses in the 1950s.
The Lionel 6-27604 carries the same safety slogan scheme as its wooden cousin. This CA-4 was photographed in the slogan scheme in 1958.
The Lionel 6-27668 from the 2011 Volume 2 catalog also carries the safety slogan scheme and was photographed in it in 1953. The cupola running board was removed by the time the safety slogans were applied.
The 6-17691 was part of the debut CA-4 offerings from Lionel in 2006. It carries a number applied to this CA-4 in June of 1959.
Lionel's 6-17699 appeared in the 2007 Volume 2 catalog and depicts a CA-4 in pool service with a more modestly sized slogan as seen in the 1960s, 70s and into the 80s.
The 2014 Lionel Signature catalog includes the 6-81841 and 6-81967. They are CA-4 cabooses renumbered and repainted in the 1970s for MOW service.
Your photos of UP scale cabooses, questions and comments are welcome and greatly appreciated. 
For an overview of O scale freight cars by type take a look at the O Scale Freight Car Guide.
https://ogrforum.com/t...le-freight-car-guide
