The Collaborative International Dictionary of English v.0.48:

Squalidness \Squal"id*ness\, n.
   Quality or state of being squalid.
   [1913 Webster]

WordNet (r) 3.0 (2006):

squalidness
    n 1: sordid dirtiness [syn: sordidness, squalor,
         squalidness]