Abstract: A row alignment system includes a plurality of row units mounted on the lift frame at the front of a harvester. One or more of the row units are transversely adjustable on the frame for alignment with the guess rows. One of the adjustable row units includes a mechanical feeler which moves in response to changes in alignment between the plant passage on the row unit and the row of crop being harvested by that row unit. A linkage connects the feeler directly to the spool of a three-position, four-way valve supported on the row unit closely adjacent the feeler. Movement of the feeler in response to row misalignment operates the valve to selectively extend or retract a cylinder to move the units to maintain the desired crop row/plant passage alignment. A manually operated valve assembly facilitates easy manual operation of the row units and permits the row units to be locked in a preselected position.