After having to rebuild much of the park after Hurricane Harvey, Mustang Island State Park opened for public use again March 1st, 2018. While the city is still working on dealing with a significant amount of hurricane damage, many of the park's amenities are available for enjoyment. Over 5 miles of coastline is open for you and your canine to enjoy, and dogs are permitted off-leash during this cleanup period, as more organized events have yet to be rescheduled and most likely won't this season. It's a great time to take advantage of this seafront freedom.
Incidentally, 11 of the 20 miles of scenic hiking trails are still open, albeit occasionally still a bit muddy. Make sure to bring good boots, and enter with the understanding that your dog is going to get dirty. Canines are welcome on these trails provided they stay on a leash. Although the park is still getting cleaned up, make sure to bring doggie bags as to avoid adding to the debris.
Camping is normally quite the popular pastime in Mustang Island State Park but will be closed until at least early fall according to park officials. The RV sites fared much better throughout the storm, and are currently still available and fully functional. For a full listing of current passable roads, please visit the Texas Parks website. Dogs are not allowed on the RV campsites.
If fishing is more your style, the shallow water fishing here is actually thriving due to the storm. Fishing these shallow, coastal areas can only be done with the proper permits. Again, during cleanup efforts canines are allowed off-leash along the shore. Park officials warn that some roads may still be impassible. Also, note that the public restrooms were destroyed during the hurricane, but temporary facilities were erected in the interim so as to help reinvigorate park use.