The 1993 Commodity Flow Survey (CFS) proved that most freight transport on U.S. highways is interstate. The nation's highway system functions principally to link the economies of states to form an integrated national economy rather than to serve the economies of individual states. Data from the 1997 CFS allow comparisons with the 1993 data to determine (a) whether the predominant pattern of interstate shipments continues as a stable phenomenon; (b) how fast the within-, from-, to-, and through-state components of truck freight are growing; and (c) whether important regional trends are evident. The shipment of freight by truck in the United States was even more predominantly interstate in 1997 than in 1993. In 1997, interstate shipments made up 76% of the total ton-miles shipped by truck; in 1993 it was 73%. The proportions of truck freight shipments originating from, destined to, passing through, or occurring entirely within a state vary significantly from state to state. Individual state distributions remained relatively stable from 1993 to 1997, with the exceptions of dramatic increases in interstate truck ton-miles in small New England states and substantial but less-dramatic increases in border states, such as New York, Michigan, Washington, California, Texas, and Florida. These findings could have important implications for highway revenue allocations because trucks carrying freight play a significant role in damage to highway pavements and structures.