Building throughout the city became very active. The widening of Broadway in the Eastern District materially affected the prosperity of that section of the city, to which Broadway became the leading business artery. Grand Street developed into a busy thoroughfare, and Fourth Street, now northern Bedford Avenue, became the third important street of this section. For a site for a new building on Broadway at Fifth (now Driggs Street), the Williamsburgh Savings Bank paid the then enormous sum of $210,000. The superb structure afterward erected on this ground is one of the most imposing in the city, its classic dome rearing itself among those objects in the city which command first attention from Bridge spectators. In 1869 it was estimated that Brooklyn had 500 miles of streets, and 150 miles of sewer. Mayor Kalbfleisch's message reported a total of 3307 buildings erected in 1868. The assessed value of real and personal property in the county was $199,840,551. But most momentous of the movements of this period was that looking to the building of the first East River bridge. The possibility of a bridge over the East River had been discussed early in the history of the two cities. General Johnson[35] had discussed the feasibility of the suggestion, and had argued that the plan was quite within the possibilities of engineering science. Thomas Pope, in a volume published in 1811, by Alexander Niven, 120 Duane Street, New York, describes his idea of a "flying pendent lever bridge," which was intensely original as well as impossible.