Fire and Discipline was originally published (in 1988) to cover tactical warfare from 1740-1850. It is now in two versions, one focusing on firepower, the other on discipline. Both versions use the same basing and organization structure. The rules are lengthy because many simple questions are answered with the clarification examples. Optional rules are included to allow for more realistic and slower play for those who prefer it. After learning the rules most players will be able to play a friendly game by using only the pullout charts.
Phil Johnson and Les Benoot offer a pdf download of fog of war rules for the horse and musket era. These are a generic add on for other horse and musket rules sets, and are intended to reflect the problems offered by visibility and scouting on command control.
Arofan Gregory offers Republic and Empire, a set of free wargames rules for 19th Century warfare.
These rules are intended to be used for any land conflict from the Napoleonic Wars through the Second Anglo-Boer War. Encompassing both colonial actiosn and conflicts between technologically advanced powers, they are intended for those who wish to recreate the lesser known conflicts of the period, for which specifically tailored rules sets are often not available. They are designed as a framework that is easily modified to fit the specific situation being recreated. Alternately, these rules are good for those who wish to play battalion-level games that move quickly, as a change of pace from more complicated games … Toward this end, any consistent basing system can be used …
Two Page 1848 – 1890 Rules is a set of free wargames rules
The Regular Army O! is a set of free wargames rules for battles of the 19th Century. It’s of a rather nebulous scale, although there is a reference to “regiments” in the rules. Mediafire rules link.