DuPont's research into polymers such as nylon, which could be formed into fibers, eventually made the braided Dacron line that was in wide use before 1938 fall out of favor.
When the thin but strong Stren brand of line was invented in 1958, monofilament began to become the fishing line of choice among anglers. It remains so today, as almost two-thirds of all fishing line sold is of the monofilament variety.
The more costly brands of monofilament are resistant to wear and tear, have superior knot strength, come in a variety of colors and are available in different strengths.
Monofilament line comes labeled as different pound tests, which reflects how much weight the line will support before it gives way. For example, 12-pound test can hold 12 pounds before it finally breaks.
An angler should always discard all monofilament line properly. If monofilament is left near the water, it is hard for animals to detect and can entangle all sorts of wildlife, leading to a slow and lingering death.