Son Lorain's death record says her maiden name was CAMPBELL. It also says she was born in Albion, Indiana.
"Ohio Deaths, 1908-1953," database with images, FamilySearch(https://familysearch.org/ark:/61903/1:1:X67L-RQ5 : accessed 23 April 2016), Lorain Allgaier, 30 Dec 1934; citing Hamilton, Butler, Ohio, reference fn 70623; FHL microfilm 2,022,232.
Hope this helps! -NGP
Yup, looks like CAMPBELL as Emma's maiden name. Here is son Campbell's marriage record.
"Illinois Marriages, 1815-1935," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:V2GP-DPF : accessed 23 April 2016), Campbell Allgaier and Maud Bartold, 14 Sep 1905; citing East St Louis, St Clair, Illinois; FHL microfilm 2,148,571.