Routing question

I am trying to add a WordPress blog to my rails app. I have installed
WP in rails/myapp/public/blog with the hope that the actual URL will
look like www.mydomain.com/blog. How do I tell rails to let WP handle
requests for everything within that blog directory or otherwise get this
to work?

Configure your web server to pass anything under /blog "around" rails and handle it via normal PHP methods.