Jeb Gleason-Allured

Greenpoint

A copy of the 1855 patent for the Bessemer process.

http://en.wikipedia.org/wiki/Bessemer_process

The Bessemer process allowed for the affordable production of steel which in turn made possible the following: large bridges, skyscrapers and railroads.

Without affordable steel, Manhattan (in particular) could never have been as population-dense as it is, nor could the boroughs be so well connected.