Ten blocks north of Post Street, it ends at an interchange with Interstate 10 (exit 360).

South of the southern terminus of SR 129, McDuff Avenue continues southward, intersecting with Remington Street, and orientates itself in a southeastern direction as a four-lane road, bordering Avondale and Riverside as it goes northwest through mostly residential streets.

Three blocks north of Park Street, it meets with Robert E. Lee High School on the western side of the road.

North of SR 129's northern terminus, McDuff Avenue continues north past US 90 and terminates on 5th Street and the Jacksonville Kennel Club.

State Road 129 once had its southern terminus at Park Street but it has been truncated back to the present southern terminus of U.S. Route 17 / State Road 15.[when?]