Here is a partial list of artillery up to 1900.
1.65 Inch Hotchkiss Mountain Gun (used at Wounded Knee)-not rotary-added sometime between 1874 and 1880
3 Inch Mountain Gun Hotchkiss-not rotary
3.2 Inch BL Rifle 1885 Model (modified)
3.2 inch BL Rifle 1890 Model
3.6 inch BL Rifle 1891 Model
3.6 inch BL Mortar 1890 Model
plus Gatling, Hotchkiss revolving cannon, Gardner and Maxim machineguns
A battery in the Massachusetts militia were using old 12pounder Napoleon muzzle-loading smoothbores until 1900 when they got 3.2 inch Breechloaders.
3 inch Ordinance Rifles from the Civil War remained in Militia Armories until 1908
In the 1880 list the only new guns listed were the 1.65 Hotchkiss, the Gatling, and the 1.45 inch Revolving Cannon (Hotchkiss). The rest were 3 inch ordinance rifles, 3.5 inch rifles and 12 pound smoothbores left over from the Civil War.
From 1902 I found this
http://en.wikipedia.org/wiki/3-inch_M1902_field_gun