A crucial step in the evolution of modern plant agriculture was the development of low-cost, energy-efficient greenhouse structures that provide optimum growing conditions year-round. In 1964, Professor William J. Roberts developed the first air-inflated double-layer polyethylene greenhouse covering system at Cook College, Rutgers University.
Structures

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Image Credit: Courtesy Flickr/Dwight Sipler (CC BY 2.0)Image Caption: A cat scales an air-inflated double-layered polyethylene greenhouse
2004

The City Plan of Philadelphia is a seminal creation in American city planning in that it was the first American City Plan to provide open public squares for the free enjoyment of the community and a gridiron street pattern featuring streets of varying widths: wide main streets and narrower side streets. In addition this plan was the first city plan in the United States to provide for long-term urban growth. These features inspired the planners of many cities to adopt the Philadelphia Plan as a model.
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Image Credit: Courtesy Wikipedia/DogearsImage Caption: The City Plan of Philadelphia pioneered many features of American city planning.Era_date_from: 1682
1996