The Hornberg fly pattern was originally created by Frank Hornberg who was the first game warden assigned to Portage County Wisconsin in 1920. Some sources say he first designed the fly in the 1920s but it wasn't until the 1940's when the Weber Tackle Company developed the fly for commercial sales that the pattern became popular. Today, it is definitely a classic pattern across the Midwest and out East.
In Joseph Bates book, Streamer Fly Tying and Fishing, (page 289) there is a paragraph about the Hornberg from the Weber Tackle Company..
Mr. Ed Wotruba, president of the Weber Tackle Company, Stevens Point Wisconsin wrote the author "This was the idea of the retired Conservation Warden Frank Hornberg when he was on active duty in Portage county. We helped him develop it, and tied the first one for commercial sale. I think he had in mind to simulate a small minnow, which this fly does nicely when fished wet. It is also very effective when dressed and fished dry. It is primarily a trout fly but takes panfish readily."
In Bates' book there is also a photo of the original Hornberg pattern (plate 1) and the complete dressing from the Weber Tackle Company, as follows:
Hook size: No. 6 regular
Body: Wound with flat silver tinsel
Wing: Two barred gray mallard breast feathers one and one-half inches long between which are the very narrow tips of two yellow neck hackles as long as the mallard and nearly concealed by it. These cover the shank of the hook, and are stroked to a point at their ends by applying a small amount of lacquer to them, rubbed between thumb and forefinger. The width of the feathers (for above size hook) is at least a quarter of an inch, with the yellow hackles narrower. (An easy way to apply the mallard is to strip the lower sides of the feathers from the quills.)
Cheek: Jungle cock, fairly long
Throat: Four or five turns of a grizzly hen neck hackle wound on dry fly style as a collar after the wing and cheeks have been applied. (This dressing should be fairly wide and heavy. The wing should not be applied too far forward, to accommodate it.)
Hornberg Special Fly Pattern (using the Original Recipe)
tied by John Simonson
Hook: Mustad 3906 #6
Body: Flat Silver Tinsel
Cheek: Jungle Cock Eyes
Wing: Two Gray Mallard Breast Feathers with Two Yellow Hackles underneath
Cheek: Jungle Cock Eyes
Throat: Hen Grizzly Hackle
If you look across the Internet you will find many variations to this old classic fly pattern, both as wet flies and dry flies with different wing colorations and in many different sizes.