Highway 523 begins at the boundary between the Hastings County and Nipissing District, east of Algonquin Provincial Park. From here the road continues south as the Madawaska Road to Maynooth, where it meets the Peterson Road and Hastings Road, all former Colonization Roads which served to open the northern frontier to settlement in the 1850s. North of the boundary, the Highway begins and is known as Cross Lake Road. It passes through a sparsely populated region dotted with lakes and muskeg, generally remaining straight, though curving sporadically to avoid the many obstacles presented by the Canadian Shield.
After passing thorough the village of Cross Lake, situated on the eastern shore of a lake with the same name, the highway abruptly curves to the east for 1 kilometre (0.62 mi). It turns back to the north and later approaches the northwestern tip of Bark Lake, on the opposite shore as Bell Bay Provincial Park. Here the highway curves to the west and follows the delta of the Madawaska River, curving north just short of entering the village of Madawaska.
^Ontario Department of Highways (1956). Ontario Road Map (Map). Cartography by C.P. Robins. Section O32.
^"Ontario Secondary Roads Now Designated 500, 600" 112 (33,119). The Globe and Mail. February 4, 1956. p. 4. "Two new Ontario road numbers appear on the province's 1956 official road map which will be ready for distribution next week. The new numbers are the 500 and 600 series and designate hundreds of miles of secondary roads which are wholly maintained by the Highways Department. More than 100 secondary roads will have their own numbers and signs this year. All of these secondary roads were taken into the province's main highways system because they form important connecting links with the King's Highways"