South Padre Island lies on the southernmost tip of Texas and is situated on the south end of Padre Island , the longest Barrier Island in the world and the largest stretch of undeveloped ocean beach in North America . It sits just 30 miles north of Mexico and is linked to the mainland by a two and a half mile long bridge, the Queen Isabella Memorial Causeway. The Town of South Padre Island is home to an estimated 5,000 people, and according to the Convention and Visitors Bureau, over one million people visit the Island every year.  It is a hotspot for retirees from northern regions to stay throughout the winter months.  These residents are known throughout the Rio Grande Valley as "Winter Texans."