The San Antonio River is a major waterway that originates in central Texas in a cluster of springs in midtown San Antonio, about 4 miles north of downtown, and follows a roughly southeastern path through the state. It eventually feeds into the Guadalupe River about 10 miles from San Antonio Bay on the Gulf of Mexico. The river is 240 miles long and cr…The San Antonio River is a major waterway that originates in central Texas in a cluster of springs in midtown San Antonio, about 4 miles north of downtown, and follows a roughly southeastern path through the state. It eventually feeds into the Guadalupe River about 10 miles from San Antonio Bay on the Gulf of Mexico. The river is 240 miles long and crosses five counties: Bexar, Goliad, Karnes, Refugio, and Wilson.