Complex sentence: One such estate was that of wealthy New York financier Thomas Fortune Ryan, in August 1887, the Ryans purchased the former Groesbeck mansion which was built in the 1860s.
Split into simpler sentences: One such estate was that of wealthy New York financier Thomas Fortune Ryan. In August 1887, the Ryans purchased the former Groesbeck mansion, which was built in the 1860s.