Evolution of the Interstate Shield

The Interstate highway shield has undergone a few revisions since its first appearance in 1958, with subsequent modifications made in 1961, 1972, 1979, 1988, and 2000 to the Manual of Uniform Traffic Control Devices (MUTCD). Some states adhere to these signage standards, while others have opted to use older shield specifications. Generally speaking, the primary changes to the shield involved enlarging the shield to accommodate bigger numerals and/or the elimination of the state name. The following table provides examples of shields that show the specifications for each year.

2di	3di	2di	3di
1958		1961
1972		1979
1988		2000