Originally spelled theatre and teatre (око 1380), from around 1550 to 1700 or later, the most common spelling was theater. Between 1720 and 1750, theater was dropped in British English but was either retained or revived in American English (Oxford English Dictionary, 2nd edition, 2009, CD-ROM: ISBN9780199563838). Recent dictionaries of American English list theatre as a less common variant, e.g., Random House Webster's College Dictionary (1991); The American Heritage Dictionary of the English Language, 4th edition (2006); New Oxford American Dictionary, third edition (2010); Merriam-Webster Dictionary (2011).
