[3][4] The navy river gun-boat Pioneer was wrecked on the Manukau bar in 1866 and one of the gun turrets forms part of the war memorial.

[6] The North Island Main Trunk railway opened to Mercer station on 20 May 1875.

The beached hulls of steamers operated until 1976 by Caesar Roose can be seen on the west bank of the river just south of Mercer.

[3] W. Stevenson & Sons Ltd bought the remains of the Roose sand dredging business in the mid 1980s[8] and, after dredging ended in 1997, redeveloped 2.5 ha (6.2 acres) of its yard with a petrol station and a food court.

The 480 ft (150 m) long single span concrete [10] Caesar Roose Bridge was opened on 18 November 1972[11] by Roose's daughter, Jeanette Thomas, with the Minister of Works, Percy Allen.