The great Chris Briem just posted the maps above and below of straight-ticket voting in the 2007 county executive race. Even in an year where Dan Onorato wasn't contested the city and Mon Valley came out for Democrats and the North Hills were solidly GOP.
For the poll watchers and sundry political junkies out there, here are some maps of straight party ticket voting from the 2007 general election, which was the last time we voted for Allegheny County Executive(ACE). The main thing to keep in mind is that race was uncontested with no Republican on the ballot at all for ACE. Whether that pushed up or pushed down the straight ticket Democratic votes I am not sure. What happened to the straight party Republican votes when there was no Republican on the ballot for ACE is one of those existential questions.