Third of four volumes of a sweeping work by the nation's leading historical geographer. The author (Geography/Syracuse Univ.) of Atlantic America (1986) and Continental America (1993) gives us another extraordinary book, this one about the impact of the acquisition of a western empire upon the US and how railways--""a space-conquering instrument of revolutionary possibilities""--helped to reknit the nation, fractured by Civil War, back together again. As a geographer must remind those (probably most) of us who are unaccustomed to thinking geographically, the realities of space and location play a central, if often unrecognized, role in any nation's history, and none more so than in American history. The result of Meinig's geographic emphasis is a fresh view. In one of many departures from conventional treatments, he shows how many Wests, not just one, came into being as the nation expanded toward the Pacific. One finds little here of the older narratives of American history and little of Frederick Jackson Turner's ""frontier thesis"" analyses of democracy and the national character. Instead, Meinig's emphasis falls on the nation's geographic reunification after 1865. Writing of ""how the United States moved into the 20th century as an increasingly integrated, unequal, stabilized and contentious set of regions,"" he also shows how it was cemented by railroads and the migration of people and integrated by new networks of institutions and new national symbols. Consequently, by the early 20thcentury, the US was able to reach beyond its continental borders toward the Arctic and into the Caribbean and Pacific, never again to be isolated in space. In characteristically powerful prose, Meinig offers a major retelling of the nation's emergence to world power.