To fit every foot American shoes are made in more than 300 sizes and widths. They range in half sizes, by groups, from infant's size 0 to a man's size 16. There are 12 widths ranging from AAAAA to EEEE, though, not all sizes are made in all these widths. Four to six widths (A-D, AA-E) for each size, however, are normally made in adult shoes for street and dress wear.
Two hundred and thirty-nine sizes and widths were required for the U.S. Army during World War II.
The great variety of styles and sizes commonly made by any one shoe manufacturer prevents the general use of mass production techniques. These depend for their success on making a large volume of identical articles. Under the simplest possible conditions the number of identical shoes made in a given factory rarely averages over 5 or 6 per cent of a day's production and in typical factories is often less than 1%.
According to legend, the size stick was invented by a monk of St. Andrews in Northampton, England.
The measurement by sizes, however, was established in 1324 by King Edward II. He decreed that three barleycorns, taken from the center of the ear andplaced end to end , equaled one inch. It was found that 39 barleycorns, so placed, equaled the length of the longest normal foot. Because 39 was divisible only by three, the longest normal foot was called size 13 and all other sizes were graded down by one barleycorn, or 1/3 of an inch to a size.
Source information is from United Shoe Machinery Corporation