<P> Starting in Indian River County and meeting the Atlantic Ocean at Duval County , the St. Johns is Florida 's primary commercial and recreational waterway . It flows north from its headwaters , originating in the direction of the Lake Wales Ridge , which is only slightly elevated at 30 feet ( 9.1 m ) above sea level . Because of this low elevation drop , the river has a long backwater . It ebbs and flows with tides that pass through the barrier islands and up the channel . Uniquely , it shares the same regional terrain as the parallel Kissimmee River , although the Kissimmee flows south . </P>
where does the st. johns river begin and end
Indian River County the Atlantic Ocean at Duval County