Travelling

 

A pattern emerges when comparing the places where the single and double l forms originate: Traveled and traveling are preferred everywhere else, but they are most common in the United States.

The primary reason lies in a particular man to us at Merriam-Webster: Webster, Noah Our lexicographical father was a big believer in spelling reform and wanted English spelling to make more sense—and if the English of his homeland had more logic than its British parent, so much the better. Brothers George and Charles Merriam bought the rights to Noah Webster's 1841 dictionary after Webster died. He came to the conclusion that both the past and present participles of travel only required one l.