SH 124 begins at SH 87 in High Island along the Gulf Coast near the northeastern end of the Bolivar Peninsula in Galveston County. SH 87 from this point toward Sabine Pass has been closed since 1990 due to coastal erosion. The highway proceeds to the north climbing up a salt dome where the central portion of High Island is located. Leaving town, the highway travels back downhill entering marshland where the highway enters Chambers County upon bridging the Gulf Intracoastal Waterway.