I have spent quite some time searching for a comprehensive list of 24-hour emergency veterinary facilities.  Most of my searches turned up lists with a combination of emergency and non-emergency hospitals, until I found the website for The Veterinary Emergency and Critical Care Society.  VECCS’s site has a clinic directory which lists the emergency and critical care facilities in each state (and even some in other nations).  You can browse the directory here or by clicking on the VECCS logo in the middle column.  I encourage you to bookmark their directory as this is a wonderful resource and can be especially helpful when you travel!