In the summer of 1864, Drew was order to organize and lead an Army expedition to size up the Indian situation in southeastern Oregon and determine if additional outposts were needed to protect immigrants. Drew left Fort Klamath on July 1 on what became known as the Owyhee Reconnaissance. His reconnaissance party was made up of 39 enlisted troops, a medical officer, and eight support personnel, including scouts, teamsters, and a blacksmith. After leaving Fort Klamath, Drew and his men proceeded to the
Williamson River, and then along the
Sprague River, following the river to its source. Drew led his party over the low mountains into what in now Drews Valley and then over
Drews Gap into the
Goose Lake Valley. The expedition traveled around the north end of
Goose Lake and then south along the east side of the lake for 21 miles until their path crossed the
Applegate Trail. At that point, Drew met several immigrant parties. Fearing Indian attacks, the civilian parties decide to follow Drew's troops. The expanded company took
Fandango Pass over the
Warner Mountains into
Surprise Valley. They then traveled northwest, passing around the north end of Cowhead Lake and over broken high desert country into the
Warner Valley. Drew's party left the Warner Valley, moving east to the Pueblo Valley, and then north to the Army post at Camp Alvord east of
Steens Mountain. The last immigrant wagon reached Camp Alvord on August 31. Because escort duty had slowed down their pace of travel, Drew had to cancels plans for exploring the
Owyhee country to the river's headwaters. Instead, Drew along with nineteen troops escorted the immigrant wagon train through the Jordon Creek Valley and on to
Fort Boise. Drew and his men then returned to Camp Alvord, arriving there on September 22. At Camp Alvord, Drew received orders to return immediately to Fort Klamath to participate in treaty negotiations with Indian tribes that had been skirmishing with settlers in the Klamath Valley and attacking wagon trains along the Applegate Trail. Drew's return route was a direct line of march from Camp Alvord to the Warner Valley. Instead of heading south to the Surprise Valley and Fandango Pass, Drew found a new pass through the Warner Mountains leading directly to the north end of the Goose Lake Valley. This new route was over one hundred miles shorter than his outbound track. Combined with the route he charted from Camp Alvord to Fort Boise, Drew cut almost three hundred miles from the original Applegate Trail route from
Fort Hall to southern Oregon. Drew successfully completed his mission, returning to Fort Klamath on October 18, 1864. However, he did not arrive in time to take part in the treaty negotiations. The peace council with the
Klamath,
Modoc, and
Yahooskin Indians had begun on October 9 and the treaty was signed on October 15, 1864, near Fort Klamath. After returning from the reconnaissance, Drew submitted his resignation from the 1st Oregon Cavalry. The reason for his resignation is unknown. On November 21, 1864, Major General
Irvin McDowell, commander of the Army's
Department of the Pacific, approved Drew's released from active duty as soon as his Owyhee Reconnaissance report was completed. McDowell also authorized Drew to return to Jacksonville to write his report. His resignation become effective on January 31, 1865. Drew's report was published in the
Jacksonville Sentinel in serial form from January 28 to March 11, 1865. It was also published as a 32-page pamphlet, which was printed in Jacksonville. == Later life ==