This paved path runs 16 miles to the coast; about one mile or less from the start is a sand trail that runs into the woods, I think a four mile loop. Nice thing about this trail is that you can peel off and head into the National Forest. The trail is pretty tech at times dependent on the weather- the paved path is leisurely, and at the end @ St Marks is absolutely beautiful.
"State Road 319 circles Tallytown, catch it and come around the south side of town to hit Woodville Hiway which will run you south. About 1/2 mile on the right is a parking lot that will begin the St Marks Trail.
http://www.singletracks.com/item.php?c=1&i=168