The Port Isabel and Rio Grande Valley Railroad was chartered on August 14, 1928, to acquire the Rio Grande Railway, which was operating between Brownsville and Port Isabel, a distance of twenty-six miles. The line had originally been constructed in 1872 as a narrow-gauge railroad but had been converted to standard gauge in 1925. The capital stock was $30,000. The principal place of business was Brownsville. The members of the first board of directors were C. R. Tyrrell, W. B. Sellers, Ada Pattee Tyrrell, L. B. Brady, C. P. Miller, V. L. Conrad, L. S. Bourne, F. W. O'Brien, W. D. Sullivan, and F. K. Matejka, all of Brownsville. In 1931 the Port Isabel and Rio Grande Valley reported passenger earnings of $5,000 and freight earnings of $10,000 and owned one locomotive and eight cars. The PI&RGV handled intrastate traffic until 1929, when it received authority to engage in interstate commerce. The road discontinued operation on December 31, 1940. The six miles from Brownsville to a connection with the port of Brownsville was sold to the St. Louis, Brownsville and Mexico Railroad, and nine miles from Port Isabel was sold to the San Benito and Rio Grande Valley Railroad, which built a three-mile connection to its existing track. Both of these companies were part of the Missouri Pacific. The rest of the Port Isabel and Rio Grande Valley was abandoned. The Missouri Pacific abandoned the Port Isabel branch in 1969. In 1990 a few miles in Brownsville remained in service as a connection with the railroad at the port.