The address of the Astoria Rr Preservation Association is: Po Box 541, Astoria, OR 97103-0541
The address of the North American Rr Museums is: Po Box 4223, Independence, MO 64051-4223
The address of the Belfast And Moosehead Lake Rr Preservat is: Po Box 535, Unity, ME 04988-0535
The address of the Abilene Smokey Valley Rr Association is: Po Box 744, Abilene, KS 67410-0744
An apartment number would be considered a unit number. PO Box is a box in a post office, and a rr is a "rural route" number most often used for way out in the countryside.
The address of the Old Colony And Fall River Rr Museum Inc is: Po Box 3455, Fall River, MA 02720
The address of the Lehigh Valley Railroad Historical Society is: Po Box Rr, Manchester, NY 14504
POB stands for Post Office Box. It is also my initials - Peter O'Brien =] Not sure about RR, though. EDITED BY SOMEONE ELSE: :) RR stands for Rural Route.
The address of the Ellsinore Branch is: Rr 2 Box 2003, Ellsinore, 63937 9532
RR means rural rout and most of the time is out of the city limits
RR in a postal address can mean rural route
The address of the Museum Of Nebraska Aviation is: Rr 1 Box 120, Kearney, NE 68847-9801