During the winter of 1862, Oliver attended the district school in Ashland, and the next spring received a certificate and in the ensuing fall became the teacher, and for four successive winters, conducted the Ashland school. In the spring of 1863, he became a member of an independent military company, the only one in Southern Oregon, a cavalry company known as the "
Mountain Rangers", to which many of the leading citizens of the country belonged. He served as a private in this company the first year, the second year as a sergeant and in the third year was chosen captain, receiving his commissions before he had reached his twentieth year from
Addison C. Gibbs, the old war governor of Oregon. In 1876, some of Applegate's friends asked to have him appointed general Indian agent for Oregon, assuming that in such a way his unusual experience in the management of Indian affairs could be used to good purpose in promoting progressive conditions to the several agencies in the state. Ex-Senator
Nesmith, who was himself a
Democrat, was an ardent advocate of the plan and wrote as follows, to Hon.
Zach Chandler, Grant's
Secretary of the Interior, with whom he had served in the U.S. Senate: "Mr. Applegate is a gentleman of culture and ability, and, unlike myself, he is a prominent
Republican and is as honest as is possible for a man to be possessing his perverted political notions. You will pardon me, I know, for proposing appointments to an administration which I do not indorse, but I do so in order to promote the reforms which you have so happily inaugurated." In 1898, Applegate took charge of the
Klamath Reservation as United States Indian agent, and served as such for five years. Congress then discontinued the position of agent and he was appointed bonded superintendent of the agency and training school, a position which he resigned after serving two years. During this period of seven years he helped establish Indian claims to over half a million dollars for lands excluded from the reservation by erroneous boundary surveys, and developed comprehensive plans for irrigation and drainage, which added to the wealth of the reservation, an area approximating in size the state of Delaware. He was identified with various enterprises looking to the development of southern Oregon, and had a reputation as a writer of both prose and verse. ==Later years and family==