In 1933, the lighthouse was automated to no longer require a human keeper and lost significance in 1934 due to the realignment of the canal at Port Colborne.

Mohawk Island is located in the eastern basin of Lake Erie in Ontario, 20 kilometres (12 mi) southeast of Port Maitland, near the mouth of the Grand River.

The island's bedrock is composed of Dundee Limestone, an Eifelian geological formation (397.5 to 391.8 million years old).

[4][5] Because of its low elevation, the proportion of the island's land area varies with lake level.

In the spring, the temperature is cooled by moist air masses from Lake Erie and remains near the freezing point.

In the fall and winter, the warmer lake water warms the air and often forms fog.

As the island is bare to bedrock and exposed to frequent heavy rainfall it is unlikely that vegetation will recover.

The Herring Gull and Double-crested Cormorant colonies on the island are the largest recorded in the eastern basin of Lake Erie.

They nest exclusively on deposits of zebra and quagga mussel shells, both of which are invasive species in the Great Lakes.

For example, the Caspian tern colony was completely destroyed in June 2010 by a large seiche that raised the water level by more than a meter in the eastern basin of Lake Erie.

During migration periods, mallards, Canada geese, goldeneyes, scaups and sandpipers frequent the Mohawk Island area as they cross Lake Erie.

[6] The lighthouse and lightkeeper's house, originally known as Gull Island, were built between 1846 and 1848 to mark the shoals near the entrance to the Welland Canal at Port Maitland.

Standing 18 metres (59 ft) high, the lighthouse has an octagonal iron lantern topped by a dome.

In 1934, the entrance to the Welland Canal was transferred to Port Colborne, reducing the importance of the lighthouse.

Access to Mohawk Island is prohibited except by permit between April 1 and August 30 to avoid disturbance of breeding birds.

Permitted activities include "wildlife viewing, picnicking, recreational fishing from shore ... [and] swimming".