Successive inventors made improved versions of this knitting machine over the centuries. In 1864 William Cotton patented the machine which was able to automatically drop and add stitches, which enabled the knitted fabric to be shaped and tailored to fit the leg.
Stockings were held up either by suspenders attached to a corset - later replaced with a belt or girdle - or by a pair of elasticated garters.
Fully-fashioned stockings are knitted flat - with the machine automatically decreasing the number of stitches as the stocking is knit towards the ankle and increasing for the foot, to create the tailored shape. The stocking is then joined at the back on a looping machine by hand, creating the seam up the back. The finishing loop or 'keyhole' at the top back of the stocking is also a result of the finishing process, and is created because the seaming machinist has to finish the seam by turning the stocking top (the welt) inside out. This is the difference between actual fully-fashioned stockings and modern "seamed" stockings (where the seam is non-functional, and is just stitched or even printed onto a finished stocking)
Until the early 20th century stockings were manufactured from wool, cotton or silk. When rayon was introduced it was used for stockings as a cheaper alternative to silk.
The next revolution in the hosiery industry came with Du Pont's introduction of nylon at the World's Fair in New York in 1939. Nylon was a revelation - just as sheer and glossy as silk and rayon but much harder wearing and without the sensitivity to getting wet. The first nylon stockings appeared in New York stores on May 15, 1940, and over 72,000 pairs were sold in the first day alone.
Unfortunately for the ladies of the day, nylon stockings were produced only for a tantalisingly brief period, as when the US joined the Second World War in 1942 the War Production Board immediately announced that Du Pont’s nylon manufacturing would be used exclusively for war materials production purposes. The scarcity of nylon stockings led many women to brown their legs and draw a seam with an eyebrow pencil; make-up companies including Helena Rubenstein even marketed "liquid stockings" for the purpose.
Once the war was over, the rush for nylons began anew, and magazines over the next decade brim with adverts for the must-have commodity.
Most people think of seamfree stockings as originating in the 1960s, so it may surprise you to know that seamfree stockings have been around longer than you might think: Hanes was marketing "no-seam stockings" as far back as the 1940s. Seamless stockings were made with reinforced heel and toe (RHT). They are produced on circular knitting machines and are shaped by tightening the stitches. They took some time to catch on, as ladies were concerned that the lack of seam line on a leg might lead observers to think she was going bare-legged, and no respectable lady would be seen without hosiery - it was considered most undignified. Hanes persisted, however, and when other manufacturers joined in, gradually - very gradually - women adopted the seamfree stockings.
Another innovation of the 1950s was a new kind of knit, "micro-mesh". Until 1945 all stockings were made with a plain flat knit, a smooth stitch that is silky and soft to the touch, with a delicate shine. Kant run and later micro-mesh knits were developed to help prevent runs in the stockings. Mirco-mesh has a smooth, matte finish which resists laddering, and was very popular during the late 50s and 60s.
Soon after, of course, came the invention of tights - which again was earlier than most people suppose. In the early 50s Ethel Gant suggested to her husband that a garment incorporating stockings with knickers would be rather convenient, and handed him a prototype. Allen brought his wife's experiment into the office, and with the help of his colleagues developed what they later called "Panti-Legs". Their new product was introduced in 1959.
They didn't catch on immediately, but as skirts became shorter and stockings by consequence less practical, tights grew in popularity. In 1970 sales of tights overtook those of stockings for the first time.
Since then of course, fashion has come more or less full circle - stockings are now on trend once more, especially for those seeking an authentically vintage look. Original vintage can be hard to find, but they are out there - I've just finished listing several pairs in my etsy shop - perfectly priced to make ideal "stocking fillers" (time to start dropping hints?).