The first Mallet in the USA was an 0-6-6-0 built by ALCO in 1904 for the
Baltimore & Ohio railroad. It was numbered 2400 and named "Old Maud".
The lack of a leading or trailing truck meant that it was only suitable
for pusher service. However, it lasted for 34 years until it was scrapped
Some of the last locomotives built in the USA were also Mallets. These
were the 2-6-6-2s built by Baldwin for the C&O.
Between these two times, railroads experimented with many articulated
wheel arrangements. Some, like the triplex or the 2-6-8-0s used on the
Great Northern were quite exotic. Others, like the Big Boy, became some
of the most famous locomotives in the world.