The branch line from Witham to Maldon in Essex was built economically during the 1840s. Two long viaducts were needed to carry the railway over the river Blackwater, built by Joseph Locke with Thomas Jackson as the principal contractor.

The longest and more northerly called Mill Stream viaduct was built some 500 ft. long and for double track over an 18 month period between 1846-7. The smaller one is 160 ft. long. In 1854 the line was singled and both bridges were reduced in width. In the 1920s the northern one was reduced in length to 150 ft by extending the embankment on the northern side.

To reduce costs, the majority of the railway was built from timber, rather than brick, although Maldon station was built to a far grander style. Sadly, a brick built goods shed on the line was demolished in mid 2008 just weeks before being considered for listed status.

Although closed to passengers on 7 September 1964 and freight on 18 April 1966 the section from Witham to Braintree remains open as the Braintree Branch Line. Approximately half a mile of the branch from Witham station toward Maldon was used as a siding serving an industrial area for delivery of steel by railway, this section closed in the early 1980s after a rail strike and is now a cycle/walkway. The section of line into the old east station in Maldon has been used as the route for a new road into the Fullbridge area. The section of trackbed linking the two former railway stations in Maldon has been used as the route of the Maldon bypass to the west of the town.

Both viaducts have survived and were restored in 1995 by Essex County Council. They are listed as a scheduled Ancient Monument.