Complex sentence: He had created 140 lots--the size he was instructed to create--of varying uniformity, and had laid out a road through the middle of them that would, eventually, become Fifth Avenue in the Commissioners' Plan of 1811.
Split into simpler sentences: He had created 140 lots--the size he was instructed to create--of varying uniformity,. The lots and had laid out a road through the middle of them that would, eventually, become Fifth Avenue in the Commissioners' Plan of 1811.