 The city is about 45 miles ( 72 km ) southeast of downtown Houston . The island is oriented generally northeast @-@ southwest , with the Gulf of Mexico on the east and south , West Bay on the west , and Galveston Bay on the north . The island 's main access point from the mainland is the Interstate Highway 45 causeway that crosses West Bay on the northeast side of the island . 
 The city <a href='drop_aux' title='1'><mark>is</mark></a>about 45 miles ( 72 km ) southeast of downtown Houston . The island is oriented generally northeast @-@ southwest , with the Gulf of Mexico on the east and south , West Bay on the west , and Galveston Bay on the north . The island <a href='null_genetive' title='2'><mark>'s</mark></a>main access point from the mainland <a href='drop_aux' title='3'><mark>is</mark></a>the Interstate Highway 45 causeway <a href='null_relcl' title='4'><mark>that</mark></a><a href='uninflect' title='5'><mark>crosses</mark></a> West Bay on the northeast side of the island . 
The city abt 45 miles ( 72 km ) southeast of downtown Houston . da island is oriented generally northeast @-@ southwest , with the Gulf of Mexico on the east and south , West Bay on tdawest , and Galveston Bay on thdaorth . Thedaland  main access point from the mainland the daerstate Highway 45 causeway cross West Bay on the ndaheast side of the island .