History of Secondary Highway 623 (#1):
The first Secondary Highway 623 was a local highway in the District of Rainy River that provided access between Highway 600 and Rainy River. Highway 623 was first depicted on a Preliminary Route Plan prepared by the Department of Highways of Ontario (DHO) in April, 1956. The route was formally designated by an Order-in-Council dated May 9, 1956. The route of Highway 623 extended north from Rainy River via the Harris Hill Road for approximately 21 miles (34 km) to Harris Hill, where the route connected to Highway 600. It should be noted that DHO's official mileage reported for Highway 623 shown above is somewhat exaggerated, as the actual length of the highway was about 27 km. Highway 623 was gravel-surfaced for its entire length and was noteworthy in that it was the highest-numbered Secondary Highway when the system of numbered Ontario Secondary Highways was originally created in 1956. The highway's route did not change at all during its brief existence. Since Highway 600 and Highway 623 shared a common terminus at Harris Hill, the DHO ultimately decided to renumber Highway 623 as a southerly extension of Highway 600 from Harris Hill to Rainy River. This change in route numbers occurred in mid-1960. Although the first route of Highway 623 ceased to exist in 1960, another unrelated Highway 623 was established in the Atikokan area in 1962.