Reference Librarian Mary Cargill suggests:

1.  NHGIS (http://www.nhgis.org/)  This is a free service from the University of
Minnesota.  Though I can’t find it on their website, the Map Division has the software,
and has experience using it.  It will map and create detailed information based on the
historical census statistics, and the students were finding it very useful.

2.  Census information.  We have the reproduction volumes in Butler Stack 2.  The population volumes are arranged alphabetically by state, and often (every one I have checked so far) there are charts for larger cities with fairly detailed statistics.  These volumes are also online in PDF, but they can be hard to search. Get the specific pages for the charts from the print volumes and then find them in the online version–this saves time.  There are also volumes for Occupations, which have some useful statistics.

3.  General histories of cities.  These can be found in CLIO under the subject, and also in WorldCat.  (NYPL has a lot of local histories that we don’t). 
City planning–[city] is also a useful subject heading.

4.  Planning documents.  Often (in every case I have had so far) cities have issued plans or studies.  These can be found several ways, and so far, I have found them using the bibliographies of the general histories, in WorldCat under the city as an author and planning or plans as a keyword, and references in PAIS.  Avery has some, and so does NYPL.

5.  Historical studies.  America History and Life has turned up some useful things, including books and dissertations.  For crime information, I have also found browsing JSTOR under Law journals has turned up some studies of crime in specific cities for the relevant years.  The hotel question is pretty much impossible, I have found.  It seems that this is local business information, and would probably be only available in city or state historical societies or archives.

6.  Sometimes these societies have material online, and Googling the city and historical society or archives or public library can help find material that they have put online.  I have found some historical maps this way.  NYPL Map Division is another option for older maps, as are general histories of cities.  (We have a WPA guide to Dallas, for example, that has a 1940 map).