No founder, sponsor or establishing record for National Strawberry Ice Cream Day has been located. The earliest archived listing found for it was captured in November 2013, and it already gives the date as January 15.
A supper list in 1863
The phrase shows up in American newspapers long before any of the rules did, and the earliest match in the California Digital Newspaper Collection is a menu. On 18 November 1863 the Daily Alta California printed a list of cakes and ices under the heading THE RUSSIAN BALL, and strawberry ice cream sits in the middle of it, beside the lemon ice cream and the meringues.
Search the same collection from 1846 and nothing comes back for the phrase before that night. The day named after the flavor leaves no comparable trail, and no founder or establishing record for it has been located.


