Although the massacre at Wounded Knee in 1890 was not literally the last battle between the Native Americans and the United States government, it is seen as the symbolic end of the Indian Wars.  There are two main reasons for this.

First, this massacre was one of the last episodes of mass violence involving Native Americans.  After this, there were only a few more scattered incidents of serious violence.  For example, there was a battle at Leech Lake in northern Minnesota in 1898.  But there were very few such incidents, making Wounded Knee the last major episode of violence.

Second, the massacre at Wounded Knee can be said to symbolize the end of Native America.  This was a battle fought by Plains Indians.  These are the Indians that are most symbolic of all Native Americans to most of us in the US today.  This was a battle that was fought because of the Indians’ believe in the Ghost Dance movement and their hope that white people would disappear.  In this way, it was a battle that symbolically marked the end of hope for the people that we tend to think of when we think of Native Americans.  For these reasons, this battle is seen as the end of the Indian Wars.