Streamers or bucktails are designed to simulate various kinds of minnows or baitfish, with the exception of those dressed as attractors-type patterns. Possibbly the most sought-after staple in the diet of any game fish is another fish. Credit for this style of fly imitation cannot be given to any specific person. Minnow imitations were being used in Britain in the early 1800s, with no documented recognition given in fly-fishing literature, as it was not recognized as a form of fly-fishing. Early settlers brought the knowledge with them in this country and primitive bucktails were tied to catch smallmouth bass as early as the 1870s. They were being offered commercially in the early 1890s.
Around 1902, fly tier Herbert L. Welch, from Maine, began tying some of our first streamer patterns. His investigative undertaking was perceptive for the time. He possibly fashioned some of the first long-shank hooks, more befitting the design of this fly.
Carrie Gertrude Stevens, from Madison, Maine, should share the limelight with Herbert Welch.  She was the wife of Wallace Stevens, who was a fishing guide. Carrie Stevens was one of the more prolific fly tiers of her time. Many of her designs live on today as a tribute to her talents and patterns. Her Gray Ghost has become famous the world over. ....
Because of the varied hook shank lengths that streamers can be tied on, one must realize that there are not real proportions standards that he or she can follow. During the glory days of the streamer in the 1940s and 1950s, most fly tiers tried to duplicate the standards set by Carrie Stevens. Were you to view a selection of her flies today you would note that she mounted the wings at the ten and two o'clock positions and they run parallel to the hook shank, instead of on top. This allows the wings to project about 20 degrees above the body. This came to be known as the "Rangeley Style." With feather wings, this obscures most of the body when looking at the fly from the side.
Some have objected to calling a streamer a fly. Their interpretation is, a streamer is a "streamer" and not a fly at all. It was only during the 1960s, when still-water fly-fishing came into vogue in Britain, that a streamer fly was even accepted into their arsenal of flies, and then only for still-water. To some, the use of the streamer is not fly-fishing. Luckily, many fly fisherman appear to be moving past this type of thinking.
The word "streamer" originaly applied to feather-wing patterns. The use of hair or bucktail for the wings is a variation that took place on a broader scale in the 1930s. To this day there are those who will not agree that a bucktail streamer is a streamer. By not understanding what a true streamer design consist of, some novice anglers have made misclassifications. To some, the Woolly Bugger represents their interpretation of a streamer. The long tail on this type of fly is just that, an extended tail on a wet fly.
With the passage of time, more and more fly fishermen are beginning to realize the importance of streamers. Some novice fly fishermen don't take the time to develop the skills needed to be successful with this fly design. ...
Some fly fishermen who specialize in the use of streamer flies consider them to be the total answer to seducing large fish. ... For those fly fishermen who can think of more than just trout, these flies are very productive on bass and other game fish. As some say, "Big flies, big fish."
The above information is an excerpt from Terry Hellekson's excellent book Fish Flies - The Encyclopedia of the Fly Tier's Art 2005.