Mustang Island, Texas USA. Mustang Island, Padre Island, Port Aransas Travel Guide. The Gulf Coast here is essentially one 131-mile-long beach, including 18-mile Mustang Island and massive 113-mile North Padre Island (the second-largest island by area in the US, after New York's Long Island). The most notable sections for beachgoers are Mustang Island State Park and Padre Island National Seashore. On the northern tip of Mustang Island, the town of Port Aransas (Ah-ran-ziss), or Port A to locals, is in many ways the most appealing beach destination on the Texas coast. It is small enough that you can bike or walk everywhere, but large enough to host loads of activities and nightlife. The pace is very relaxed, and daily life is dominated by hanging out on the beach, fishing and doing nothing perhaps followed up by a few cold drinks as the sun goes down.