We reached Washington Beach from Matamoros on July 6, and drove to a point approximately 33 miles south on the beach, where we made Camp 1 on the east side of large dunes 400 yards from the surf. From this camp we worked the beach and dunes and also visited alkaline flats adjacent to the Laguna Madre. On the afternoon of July 8, we drove south along the beach and established Camp 2 on the south side of the Third Pass, approximately 73 miles south of Washington Beach. We had intended to go farther south but were unable to cross the Fourth Pass, an inlet three miles south of the Third Pass. We left the barrier island on the afternoon of July 10, after driving north from Camp 2 to the mouth of the Rio Grande, 11 miles north of Washington Beach.

Mexican fishermen camped at the Fourth Pass told us that, had we been able to cross the Fourth Pass, it would have been possible to drive south on the beach all the way to La Pesca, a fishing village near the mouth of the RÍo Soto la Marina, approximately 150 miles south of Washington Beach.