Samuel James Renwick McMillan (February 22, 1826 – October 3, 1897) was an American lawyer, judge and Republican politician.

His parents Thomas Long and Jane McMillan (née Gormly) were of Scottish and Irish ancestry.

During the Dakota War of 1862 McMillan served as a Second Lieutenant in a militia unit known as the Stillwater Frontier Guards which was only briefly active.

[5] Ravi D. Goel collection of Samuel James Renwick McMillan family papers, 1818-1956, Minnesota Historical Society.

These papers span five generations & include a direct connection to the Revolutionary War and the 1890 Battle of Wounded Knee.