The island is approximately 13 kilometres (8 mi) northwest of Portadown.

The island is also regularly the home of wintering and breeding birds.

In 1802 work started under the direction of Daniel Monks to excavate a short channel from the eastern bank of the Blackwater straight to the lough shore through the lower section of Derrywarragh Peninsula thus turning it into what is now Derrywarragh Island.

According to Craigavon Museum Services, it was probably a "watchtower to protect the mouth of the River Blackwater".

[3][4] The island is also the home of Maghery Sean MacDermott's GAA club.