The original Hawkesbury River Rail Bridge was constructed between 1886 and 1889. The current bridge was rebuilt in 1946, after the Second World War. But the first Hawkesbury Railway, or Brooklyn, Bridge was the largest such civil engineering construction in the Southern Hemisphere at a phenomenal 862 metres. It was even the topic of a paper at the Institution of Civil Engineering in London in 1890. One of its piers, at 162 feet below water level, was, at the time of its construction, the lowest depth ever attained for a bridge foundation. The cost was over 327,000 pounds just to replace the ferry crossing, previously the only means of travellers from Sydney reaching Woy Woy, Gosford, Newcastle and indeed Brisbane. The bridge made the last really tough rail section complete and the Hawkesbury River to Mullet Creek (Wondabyne) rail line opened in 1889
Woy Woy tunnel was thought likely to be the major hold-up on the Sydney to Newcastle line. It was certainly a massive undertaking back in the 1880s. It is nearly 1.8 km, over a mile long, and needed nearly 95,000 cubic metres of rock excavating which took 110 tons of blasting powder and 10 tons of dynamite. The 800 construction workers had to lay 10,000,000 bricks using 10,000 casks of cement. Construction commenced on 8th March 1884 and finished on 17th July 1886. So in the end, the tunnel was finished a year before the Brooklyn Bridge entered service on the 16th of January 1888.