Twenty-First Century Limited

For this one, I chose to blend shapes and numbers together to form the mark. Two circles + one block = 2 + 1 = 21.

It didn't make any sense to keep the mark as Twentieth Century as we've now incremented a century.

A bit about Twentieth Century Limited:
(from Wikipedia)

The 20th Century Limited was an express passenger train on the New York Central Railroad (NYC) from 1902 to 1967, advertised as "The Most Famous Train in the World".[1] In the year of its last run, The New York Times said that it "...was known to railroad buffs for 65 years as the world's greatest train".[2] The train traveled between Grand Central Terminal (GCT) in New York City and LaSalle Street Station in Chicago, Illinois, along the railroad's "Water Level Route".