I collected the names of every horse to ever compete in the Kentucky Derby, Preakness Stakes, or Belmont Stakes between each race's inception and 2014. Going back all the way to 1867, when the first Belmont was won by Ruthless, there have been more than 3,200 horses to race in a Triple Crown event...The Slate article has a list of the 111 longest names, the shortest ones, and some grammatically troublesome ones.
Then, starting in the 1960s, the names started to grow to their current lengths—just under 11 letters on average. It may not sound like a huge change, but it's an objective measure of the growing eccentricity of names...
Names can be rejected by the Jockey Club, which as a current rule sets the limit at 18 characters. Since this rule was created, four horses have reached that limit without the help of spaces or punctuation marks: Lookinforthebigone, Atswhatimtalknbout, Imawildandcrazyguy, and Sweetnorthernsaint.
18 May 2015
Slate has an article about the increasing length of the names of racehorses: