Signed languages are incredibly fluid. Grammar order (more like English, or more quote-unquote 'pure' ASL style?), nouns and verbs (drive 100 miles in any direction, and at least some signs will be different with the locals), even 'accents' based on city, race, culture.

What's really amazing about it is that despite this, someone very fluent in Sign can usually communicate with locals very quickly, and pick up the local signs in a short time.