Firstly, The Brooklyn Army Terminal is definitely not abandoned, in the building there is a middle part that could be called "abandoned". The other parts of the building is now office spaces for small companies. Three railroad tracks go through the space in the warehouses and two track went through the center (as seen in the photographs). This building has rich history with the army, World War 2 and even with the prohibition.
During the prohibition, they had two vaults containing alcohol and narcotics and later they were thrown in incinerator, to get rid of all the illegal substances. After thefts from the vaults, they constructed one of the biggest vaults for storage of drugs. They also had a lab that tested the chemical makeup of the alcohol. In 1928, they tried to convert it into a barrack, that could hold 500 residents while they were transferring bases. The military built a 125 person prisoner, and would house people convicted of high crimes in the army. It was also a base for shipping during World War 2 and 3.5 million soliders passed through the base during this time. After World War 2, the Brooklyn army terminal became one of the safest ports in the United States and 200,000 soldiers departed from the port each year. The United States Department of Defense announced in May 1964, that it was thinking about closing, Brooklyn Army Terminal, Fort Jay and the Brooklyn Navy yard to save money then they announced a few months later that the Brooklyn Army Terminal along with hundreds of bases would close and operation would move to New Jersey. Big army ports just like Brooklyn Army Terminal, are now renovating and being repurposed for new New York companies.
This building is a active office building it is not abandoned. You are allowed to go and explore the middle part now though.