sentences:  According to the United States Census, Blackford County's population peaked at 17,123 in 1900, and it still has not returned to that zenith over 100 years later.The end of the gas boom was especially difficult for the smaller communities in the county, since the loss of a single business has more of an impact on small communities.In the case of Millgrove, the community's major manufacturer (a glass factory) closed.