Listed alphabetically below are the 122 cities which serve as the units of analysis in the empirical portions of this study. They are the universe of cities in the United States with 25,000 or more inhabitants in 1890. The group originally numbered 124, but two places returned separately in the 1890 Census–Brooklyn and Long Island City, New York–were consolidated, under the Greater New York Charter of 1898, into boroughs of the City of New York. Formerly autonomous Brooklyn became one borough, whereas Long Island City was combined with several other municipalities to form the Borough of Queens. Statistics for Brooklyn and Long Island City in 1890 have been added to those of New York City in that year to simulate a geographical unit comparable to the New York of 1906.

Other cities as well grew by consolidation during this period, but the annexed areas were too small to have been returned as distinct urban places in the 1890 enumeration of religious organizations. Thus, data with which to make desired adjustments to religious measures are not available from published Census sources.

Data on changes in land area between 1890 and 1910 could be located (in McKenzie, 1933: 336–339) for 73 of the largest cities in the sample. Twenty cities experienced no growth in area during this period. Of the 53 cities that did add territory, the median increment was 6.4 square miles. These figures appear to validate Victor Jones's (1953: 551) observation that there occurred “few significant annexations after 1890” and before the immediate post-Second World War years.