The Ivory City — Emily Bain Murphy

The St. Louis World's Fair, 1904: A miniature city of palaces and pavilions that becomes a backdrop for romance, betrayal -- and murder.
     Cousins Grace and Lillie have been best friends since birth, despite Grace's vastly inferior social status ever since her mother married for love instead of wealth. When Lillie invites Grace to the biggest event of the century -- the legendary World's Fair, also known as “The Ivory City” -- Grace hopes her fortunes might be about to change.
      But when a member of their party is brutally killed at the fair, and suspicion falls on Lillie's brother Oliver, Grace must prove Oliver's innocence before her beloved cousins' family is ruined forever. Along the way, she'll discover that the city's wealthy elite -- including Oliver's handsome but irritable friend Theodore -- aren't quite who they appear to be. And amidst the glitz, glamor, and magic of the Ivory City lurks a danger that just may claim her life.