M1816 & M1817 as well as Halls were in use still in Flintlock as late as Shiloh.
Shiloh just might be one of the last if not THE last major battle in North America fought with flintlocks.
19th Tennessee CSA--although they may have gotten some caplock smoothbores just before battle.
12th Tennessee CSA had caplock and flintlock muskets
14th Tennessee CSA
20th Tennessee CSA had flintlocks until March 1862, then went to Enfields
22nd Tennessee may have had English muskets and some flintlocks.
23rd Tennessee CSA
24th Tennessee CSA ostensibly had 1841 Mississippi rifles and flintlock .69s.
28th Tennessee CSA had a mix of modern P53 Enfields and flintlock .69s.
33rd Tennessee had flintlocks, apparently to augment civilian hunting guns and shotguns
15th Tennessee had a mix of caplock and flintlock .69 smoothbores, apparently
6th Tennessee had a mix
So to the 9th TN also.
The Crescent City Infantry had a bunch of smoothbore muskets, 1819 Halls, and shotguns.
Apparently some un-modified flintlock Halls breechloaders were use by the 2nd, 6th, 7th, 10th Arkansas Inf.
3rd KY CSA had a mix of caplock and flintlocks.
15th Mississippi had a mix of rifles and smoothbores, including flintlocks.
Lots and lots more percussion converted flintlocks.
The last use of flintlocks in major battles in South America must surely be during the 1864-1870 Paraguay War or War of the Triple Alliance when Paraguay was decimated by Imperial Brazil, Argentina and Uruguay... Certainly large quantities of India-pattern British flintlock muskets had been sold to Paraguay after the Napoleonic Wars into the early 19th Century.
The 7th Texas showed up in Tennessee with 750 men. Their arms consisted of 123 shotguns--of which, 25 were in need of repair--150 miscellaneous "rifles"--48 in "poor condition"--and 104 percussion muskets
given to them while they marched through Louisiana. A total of 377 weapons for those 750 men.
By August 1861
Tennessee had raised 17,541 infantry of which
69 percent were armed with flintlocks, 20 percent with smoothbore percussion guns, and 11 percent with rifles.
Apparently the 47th TN had 10 different makes and models of firearms in their possession!