"Linear feet" is the standard measure of archival material, because it helps the archivist know how much shelf space is needed for a collection.
One linear foot is about the size of one standard records box (left) or two smaller document boxes.
Porter Campus
1801 Massachusetts Avenue
Cambridge, MA 02140
617-349-8070
South Campus
89 Brattle Street
Cambridge, MA 02138
617-349-8850