There's no comprehensive master list of every board game released in 1915 — the industry wasn't tracked like today. But historical records and trends give us a clear picture of what people were playing.
Chess, Checkers, Dominoes, and traditional card games (Euchre, Hearts, Whist) were household staples.
Simple race games, dexterity puzzles, and story-based board games for kids were common. Many were handmade or produced by small publishers like Milton Bradley and Parker Brothers (early years).
With WWI raging, patriotic and tactical war games appeared. Examples include The Game of War (UK) and various trench-warfare simulations sold as parlor novelties.
While a complete list is lost to time, these resources can uncover forgotten gems from 1915.