Route 89 starts at an intersection with Route 100. Shortly after, it intersects with Route K. Then as it goes south, it intersects with Route FF. Then it intersects with Route HH. Further south it intersects with Route J. Then it branches off a spur route of Route 89. Further south, it intersects with US 50. US 50 is shared with Route 89 until an intersection in Linn. Then it continues south and then it intersects with Route E. Several miles south it intersects with Route D. Then it intersects with Route Y outside of Belle. Shortly after, it crosses over into Maries County and ends at an intersection with Route 28 in Belle.
Route 89 Spur/Route 89Y is a highway that forms the eastern leg of a Y intersection between Route 89 and US 50 in Osage County. Southbound Route 89 travelers wishing to connect to eastbound US 50 can savenearly of travel by utilizing Route 89 Spur rather than making a direct connection between the two highways at Potts.