Mrs. Bierman did not compile this herself; it was probably done in the 1970s or 80s, as the index also covers four scrapbooks compiled by local history buff Bob Warn, who died in 1977. The Warn scrapbooks are now in the keeping of the Northfield Historical Society and are not currently available online.
I cannot verify how complete or accurate the index is, but it does list about 500 names of Northfielders. Add this index to the full-text searchability of the nine volumes, and you’ve got great odds of finding someone if they’re mentioned.
The index is alphabetical by name; the reference from there is to a scrapbook (see their naming code on the first page) and a page in the scrapbook. Note that these page numbers are the ones written in pencil in the corners of the scrapbook pages.