Conversation so far:
What was Frederick Law Olmsted's involvement with central park?
Frederick Law Olmsted and Vaux entered the Central Park design competition together.
Did Frederick Law Olmstead and Calvert Vaux win the central park design competition?
Frederick Law Olmstead's and Calvert Vaux's Greensward Plan was announced in 1858 as the winning design.
What was special about Olmsted and Vaux's design for Central Park?
The design of Central Park embodies Olmsted's social consciousness and commitment to egalitarian ideals.

Question: when was their design actually implemented?
Self-contained rewrite: When was Olmsted and Vaux's Central Park design actually implemented?