Who did NYSE merge with?

Can you tell me, in a succinct manner, who the New York Stock Exchange (NYSE) merged with? I'm curious to know if this was a strategic move to expand their operations or if it was a response to a particular market trend. Also, how did this merger impact the overall financial landscape and the investors who were previously associated with both entities? It would be helpful to understand the rationale behind this decision and the potential consequences it may have had on the industry.