This is the view of the bridge and the heights behind it from the side of the creek where Union troops attacked.  After they finally took the bridge, once again there was a chance to completely destroy Lee's army, but the last minute arrival of A.P. Hill and his Division was able to stop Burnside's advance on the town of Sharpsburg. 
Over the course of the day little ground had been gained.  The casualties on both sides were tremendous.  Still Lee stood his ground.  On the 18th both armies stared at each other without resuming the battle.  On the 19th Lee retreated, leaving the field to McClellan.  Lee's invasion was a failure.  Few recruits joined the Rebel army, there was no foreign recognition of the Confederacy and the men Lee lost were not replaceable.  Several times, McClellan could have won a smashing victory, but it was beyond him.  It was left to Lincoln to win the battle.