Indian wars were fought throughout the western regions, with more conflicts in the states bordering Mexico than in the interior states. Arizona ranked highest, with 310 known battles fought within the state's boundaries between Americans and the Natives. Arizona ranked highest in war deaths, with 4,340 killed, including soldiers, civilians, and Native Americans. That was more than twice as many as occurred in Texas, the second-highest-ranking state. Most of the deaths in Arizona were caused by the Apache. Michno also says that fifty-one percent of the Indian war battles between 1850 and 1890 took place in Arizona, Texas, and New Mexico, as well as thirty-seven percent of the casualties in the county west of the Mississippi River.