A superb pair of maps that depict the trolley lines (top) and elevated and subway lines (bottom) of the Brooklyn Rapid Transit (BRT) Company as they would appear after the work specified in the famous “Dual Contracts” agreement was completed. Much of today’s existing subway system came about because of this contract, as can be seen from the red (proposed) lines on the lower map.

For me, the top map is even more interesting – it shows how incredibly dense the trolley system in Brooklyn was at the time.

Source: University of Texas Library map collection