A toolbar transport system for extending and retracting a large agricultural toolbar. Forward and rearward folding segments of the toolbar allow the toolbar assembly to retract against the sides of the vehicle without interfering with the steering wheels. A forward-folding segment and rearward-folding segment of each lateral toolbar section connect to provide steering wheel clearance in the transfer position and an integrated lateral toolbar with regularly-spaced ground-engaging implements in the application position. Gauge wheel assemblies assist in the extension and deployment of the toolbar assembly.