The boundary lines of Union County are as follows: Beginning at the mouth of the Olustee Creek; thence northerly up the thread of said creek to a point where said creek is intersected by the middle line of township four south, range eighteen east; thence east on said middle township line, concurrent with the south boundary line of Baker County to a point where the bed of New River intersects said line; thence following the meanderings of the thread of said New River in a southwesterly direction to the thread of the Santa Fe River; thence northwesterly down the thread of said Santa Fe River to the mouth of Olustee Creek and the place of beginning.