When did Horizon start?

Could you please elaborate on the timeline of Horizon's inception? Specifically, when did the idea for Horizon first come to fruition, and what were the initial steps taken to bring this concept to life? Additionally, was there a particular event or catalyst that sparked the creation of Horizon, or was it a gradual evolution of an existing idea? It would be insightful to understand the historical context surrounding Horizon's origins and the motivations behind its founding.