Complex sentence: The Burnham Plan is an essay principally authored by Daniel Burnham in 1909 titled The Plan of Chicago in response to a request by the city's social and business upper crust for a detailed city Plan.
Split into simpler sentences: The Burnham Plan is an essay, principally authored by Daniel Burnham in 1909, entitled The Plan of Chicago. The essay was written in response to a request by the city's social and business upper crust for a detailed city plan.