Conversation so far:
what was Olmsted's involvement with central park?
Olmsted and Vaux entered the Central Park design competition together.
did they win the central park design competition?
They were announced as winners in 1858.
what was special about their design?
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's and Vaux's design of central park actually implemented?