Most of the what-ifs were culled by the authors, both of them architectural critics and historians, from 19th- and 20th-century and contemporary blueprints. They will be featured at the Queens Museum next year in an exhibition (with, one hopes, a more welcoming typeface). Among them:
James E. Serrell’s ambitious 1865 plan to expand Manhattan by rerouting the East River to a new canal farther east.
Gustav Lindenthal’s gigantic engineering vision of 1887 linking Manhattan to mainland America across the Hudson River, from West 23rd Street.