The Auglaize River rises in southeastern
Allen County, approximately southeast of
Lima and north of
Indian Lake. It flows southwest to
Wapakoneta, then generally north in a zigzag course, past
Delphos,
Fort Jennings and
Oakwood. It joins the Maumee from the south at
Defiance, approximately east of the mouth of the
Tiffin River at . It receives the
Ottawa River from the southeast in western
Putnam County, northwest of Lima. It also receives the
Blanchard River in western Putnam County. It receives the
Little Auglaize River from the south in eastern
Paulding County. It receives
Flatrock Creek from the west in northeastern Paulding County. A portage from the headwaters of the Great Miami River to the south bend of the Auglaize made it part of an important link between the watershed of the Ohio (and the Mississippi) and Lake Erie and the St. Lawrence watershed, heavily settled in pre-Columbian times. During the days of the
Ohio Country in the 18th century, the area around the river was inhabited by the
Ottawa. During the mid-1790s, the area near the mouth of the Auglaize surpassed Kekionga to the west as the center of Indian influence.
Fort Defiance was constructed in 1794 near the confluence of the Auglaize and the Maumee by General Mad Anthony Wayne.
Fort Amanda, constructed along the river southwest of Lima in 1812, was an important American outpost during the
War of 1812. ==Variant names==