The US Military made demands to their counterparts in Spanish Florida to return the escaped slaves to their owners in the US and destroy Negro Fort, The Spanish refused to answer and plans were made to attack the fort.
Col. Clinch led his infantry and surrounded the landside of the fort and ordered them to surrender, their answer was to open fire with their artillery. On July 27, 1816 US gunboats moved up the river and opened fire on the fort, after a short exchange of artillery, one of the US rounds, a heated canon ball, went through the open door of the powder magazine causing hundreds of kegs of black powder to explode instantly destroying the entire fort. Over 270 men, women and children died in the explosion.
In 1818, Lt. Gadsden was ordered to rebuild the fort; he built his fort inside of the earthworks of the original British post and named it Fort Gadsden. Years later during the Civil War the Confederates used the fort until an outbreak of malaria forced them to leave.
The earthworks still remain for both the British Post and the US Fort, they have an nice interruptive center there and a trail which take you to the Renegade Cemetery, where there are the remains of a small brick tomb where the dead from the explosion where buried.