Horseman #9 - Ride from Van Horn to Blackwater without touching any water.
Go to the stables near Van Horn and get a Horse Care Package before setting off.
Set off from the Stagecoach sign in Van Horn in the morning time so you have plenty of light to see other traffic on the roads and avoid it.
Feed and brush the horse before setting off.
Stock up on Potent Horse Stimulant / Horse Stimulant.