Q. When did Manhattan’s rectangular street grid first begin appearing?

A. The rigid right-angled grid that defines most of Manhattan was officially adopted in 1811. But its hallmark regularity of design began appearing in new blocks laid out in the 1740s.

“Manhattan in Maps: 1527-1995,” a 1997 book by Paul E. Cohen and Robert T. Augustyn, reproduces and discusses a map of the city in 1754 (at right) that was prepared by Francis Maerschalck, who had a long career as the city surveyor. It shows three areas of new growth: the area just north of the modern site of the World Trade Center; the section that would become Little Italy, just north of Canal Street; and a group of blocks to the southeast, by the East River.

All three sites show more structured growth than the winding streets of the Dutch era. Familiar streets that appear on this map for the first time include Mott, Mulberry, Hester, Bayard, Church, Vesey and Dey.

The two new sections north of Canal and along the East River appear to have been the earliest instances of the systematic development of land for profit, the writers said.