These indexes appear to have been created by different agencies and for different purposes. While some may have actually been produced by the Common Council as indexes to the ordinance books themselves, others seem to have been put together by the Mayor's Office and other departments. At least one of the index volumes was actually created during the Union occupation of the city by the Bureau of Finance, apparently to enable officials in that office to find laws on specific subjects. Whatever their origins and purposes, these volumes do act as useful finding aids to at least a portion of the ordinances/resolutions. The indexes have been arranged chronologically (although dates are approximate only) regardless of their provenance (which is impossible to ascertain is some cases anyway).