Yes, nearly all large American cities annexed smaller settlements as they grew in the 19th century. Of course, the main settlement (typically near a harbor) primarily grew outward by “additions,” but often there were small trading centers a few miles distant that ended up being absorbed if the city grew enough. The names are different in every big city: Boston absorbed Charlestown, Dorchester, and Roxbury—but not Cambridge. Philadelphia’s 1854 consolidation brought in Germantown, Frankford, and others. A big consolidation in 1889 quadrupled Chicago’s area overnight as it absorbed four adjacent suburbs. This so concerned New York that it moved toward consolidation of what we know as the modern five-borough city, absorbing not only Brooklyn and smaller towns such as Flatbush, but still-rural boroughs like Queens and Richmond that had outlying independent settlements separated by farmland. The story is the same all across the country, with overly optimistic entrepreneurs platting competing townsites in any location with a promising geographic situation. Even places like Dallas, still of modest size in the early 20th century, eventually outstripped and absorbed Oak Cliff; Denver subsumed Auraria; Seattle took in Ballard, Columbia, and West Seattle. The quintessential 20th century city, Los Angeles, was really an archipelago of independent settlements from San Fernando to Palms to San Pedro to Watts that were linked together by interurban railway and county highways, and eventually lured into the city with promises of plentiful water, better infrastructure, and more professional policing.

In many states, changes in the political situation and state law in the first two decades of the 20th century allowed suburbs to more easily decline annexation and still provide local services such as fire protection and good water supplies. As state law allowed small municipalities more power and more bonding authority, increasingly they chose to stay independent of Chicago or other big cities, with their corruption, their open saloons, and their Catholic immigrants. The contrast of lifestyles and politics were important factors as the postwar housing boom covered much of the countryside with new houses. The builders and owners of those new houses sought services from existing small towns, and when that wasn’t practical (or they were rebuffed) they typically founded new municipalities. Only in the Sunbelt was very much postwar growth annexed to cities like Houston, Phoenix, or Charlotte.

The situation in the Tri- (later Quad) Cities resulted from a combination of natural barriers, such as the river bluffs, and dispersed industrial anchors. None of the cities on either side of the river/state line grew large enough early enough to outshine and absorb the others.