It is getting a little cliche, but a traditional knife just has that "feel", if it looks like one, it is. My great great Uncle Chick, who used to ride his horse from Baltimore to the area my immediate family lives in now (N MD), carried a sawed off double on his leg. This was the 1920's/1930's. He had a nice gun collection, and I'm sure he must've had some great knives too. He got around, and he would've known a real sheath knife if he had seen it.
The Hudson's Bay camp knives were heavily used, at least in the far north, during the 1800's. Repurposed kitchen knives, reshaped by men heading west to make their fortunes in the American fur trade. The infamous bowie, the 1911A1 of the time

. The Marble's Woodcrafter and Buck Woodsman style knives over the last 85 years. Lots of great craftsmen like Matt Liesnewski and Mike Mann are bringing a lot of the old fixed blade patterns back, and let me tell you, they are not wall flowers. A lot of custom makers have brought back some neat, useful patterns designed by wilderness writers Nessmuk and Horace Kephart, the Nessmuk and the Kephart. I've seen some of these models with stainless steels and micarta scales, heck, I just ordered a Kephart with S35VN blade and micarta scales. My order is not a true traditional, but the blade shape and handle shape are. The Kepharts I have with A2 blades and cocobolo scales are traditional.
Backwoodsman and Tactical Knives writer Dan Schectman recommended a book called Knife in Homespun America by Madison Grant, in an article for Backwoodsman, and told me in person to pick up a copy. This book is extremely hard to find in stores, you won't find it in Barnes and Noble and probably not the used bookstore. I did get a copy from an online muzzleloading dealer. This book has old photographs, and line drawings, of knives that Grant encountered. These were riflemen's knives, mountain men knives, and just plain old knives of great design, made by the farm blacksmith, or by the blacksmith in town. Lots of neat, useful knives.
In the cities, the small cheaper barlows or no frills jack knives might have appealed to the every day user. Out in the country, whether you were in the mountains or working the fields, you carried a fixed blade.