Ok, source material for American Primitive knives, excluding trade knives, bowies, and daggers... First of all, the caveat: I'm not any kind of expert on the subject - I don't even collect old knives - just a guy that read a couple books on the subject trying to figure out if an 18th century blacksmith knife ever existed and if so what it could look like. My primary interests is 1) making stuff that is authentic as possible and 2) mostly the 18th century, not 19th. My take on what are useful resources is going inevitable reflect that focus, particularly since a lot of my stuff is in storage and I have to go on memory just now.
There ain't much in terms of analytical material, mostly because datable examples are so rare. The best book on the subject is Gordon Minnis's American Primitive Knives, 1770-1870. It is the best resource out there not because it has the most pictures, but because Gordon is fairly selective and includes things like construction details, provenance if any, and at least some explanation as why he assigns it a certain date and how confident he is. Current scholarship suggests that he is wrong in his belief that commercial knives were rare or expensive in the early years of this country, but it gives at least a starting point to someone trying to get a handle on what might have been produced when. It also includes the Fort Ticonderoga knife, which is a solidly datable (1778) example of an 18th century homespun knife. Unfortunately it also is out of print and quite expensive when available (I don't own a copy, myself) but is available via Interlibrary loan for those of you who have library systems that still cater to those that like to read books...
The rest of the books I am familiar with are primarily picture resources, aka data dumps, from which you must sort the wheat from the chaff, so to speak, depending on what period you are interested in.
If you can't get ahold of American Primitive Knives, and even if you can, Johnson's Accouterments III has an abbreviated (two pages) essay by Minnis followed by many, many photographs from Minnis' collection, including a bunch that didn't make it into his own book. Minnis, wisely, does not attempt to date any of these knives and he doesn't give as much detail as he does in his other book, but as a source of inspiration/eye-candy/study-material-for-shape-etc it is a great resource, particularly since it is still readily available at a reasonable price from ToTW and no doubt others.
Madison Grant's The Knife in Homespun America is pretty familiar to most folks and is the first book I read on the subject, and he has a lot of really interesting old knives. Unfortunately he tends towards "atmosphere" instead of analysis and his dates should be taken with a huge grain of salt. The best way to use it, I think, is to start by looking through it, reading the captions, and figuring out which knives have a known history or distinctive features that mark it as belonging to particular period, and use those handful of examples as starting points.
George Neumann's Swords and Blades of the American Revolution also has a number of old knives, but while I love that book in general I do not love the homespun knife section - he doesn't have any firmly datable examples and he doesn't really try to give them useful dates, opting instead of for a range that could be as late as the mid-19th century (and even there may be a bit too optimistic!) Some cool examples - the example made from an old scythe handle is great - but not a great place to begin. It is worth getting for 1) swords 2) bayonets 3) axes 4) polearms and 5) dirks, folding knives, and daggers - everything except the blades under discussion, as a matter of fact! Only thing it ignores is trade knives with only one example....
I was asked via PM specifically about Appalachian knives. Since that hasn't been an area of interest I can't say much about them, except that there is only one - a bowie-type - in Guns and Gunmaking Tools of Southern Appalachia - and that there are a number of ranging from little utility/patch knives to big fighting knives in Webb's Sketches of Hunting Pouches, Powder Horns and Accoutrements of Southern Appalachia. Basically a regionally-specific, hand-drawn version of Madison Grant - I don't take his dates as gospel but the pictures are nice to look at.
The underlying problem with all these books is that plain ole' hand-made, one-off, homespun knives are simultaneously are all different and yet don't lend themselves to falling into patterns that would allow us to date them by shape or decoration like we do rifles. Apart from a handful that are dated, dug up from archeological contests that prove a firm date (like the one dug up from a fortification made in 1778) or have other provenance, there just isn't much to work on.
So, you may ask, how does one sort out which knives are likely later than 1860, and which are likely earlier? One place to start would be to look at commercially produced knives, on the assumption that anyone making a "one-off" would have been influenced by the knives around him. Remember that they didn't have the internet back then, and prior to Bowie knives were mostly tools, not fashion statements. Blade shape is one obvious area - no one was manufacturing clip points in the 18th century, so a knife with that feature probably dates post-1820 (I think). A stick tang could have been made at any time, but a scale handle with 4-6 pins or more is post 1800, since that was a style that came in the 19th century and fell out of favor by the Civil War (I think - take my dates with a grain of salt too!). 18th century trade knives used iron pins, fairly thin ones, so anything with brass pins is probably later I think and if it has cutler's rivets it is definitely later - I'm unsure of the exact dates but I'm pretty sure that cutler's rivets post-date the Fur Trade. OTOH, pistol grips show up on 18th century table knives, including the cartouche knives traded by the British to the Indians 1780-1800, so I'm inclined to to date any knife with a pistol-grip handle fairly early absent something pointing a later date (like rivets....)
Once you have a couple examples that can be dated by provenance or features to the area you are interested in, you can look at commonalities. Since I am interested in 18th century knives, I note in particular that Grant has a couple of middling-sized knives with a reasonable chance, IMO, of being period - the one found on the Paoli Massacre Site and the pictured next to it with a pewter lion-headed handle. Both have upswept blades with fairly blunt spear-point tips - what I call a banana-shaped blade - and a rat-tail tang. The Fort Ti blade pictured in Minnis' book also has a banana blade, albeit much more subtle (all the repros I've seen miss that feature and just give it an upswept tip) and a rat-tail tang. No handle survived, but Minnis says that lab analysis indicated that it was bone or antler. I then note another knife from Minnis with a pistol-grip handle (reminiscent of a 18th or early 19th century eating knife), a scalper-type blade, and a stick tang, and recall that Don Troiani has a knife with a sheath dated 1759 and it has a stick tang, antler crown handle, and a curved blade (mostly hidden in the illustration, alas)....So I conclude that a curved blade, either banana-shaped or scalper-like, and stick tangs are plausible forms for an 18th century knife, with either antler or wood handles. No pewter bolsters, and only one has an iron ferrule while another has, IIRC, wire wound around it's handle as a ferrule (something I've seen on another bonified 18th century knife, a French butcher knife with its handle carved into an effigy by its Native purchaser).
I think that there is a lot of room for creativity when make reproductions. The pitfall I think most people fall into is making knives that too nice and too influenced by modern art knives in shape. Looking at old knives a lot will help tame this, I think - even the ones that aren't datable to the muzzleloading period are useful for this, because they show how someone uninfluenced by the modern knife scene shaped knives and help us get into the heads of an earlier generation, if you understand what I mean. If folks are having trouble figuring out the differences try drawing a couple knives to scale freehand - drawing forces you to look at lines and proportions differently than you might otherwise. My discovery that the Fort Ti knife had a slight banana/drop point shape instead of a simple upswept tip came about while I was trying to make a scale "blueprint."
