Moving northwestward, the cyclone quickly intensified into a strong Category 4 hurricane on the modern-day Saffir–Simpson scale by the following day.

Late on August 10, the hurricane made landfall on Last Island, Louisiana, with winds at 150 mph (240 km/h), hours before striking near New Iberia.

A storm surge between 11 and 12 feet (3.4 and 3.7 m) completely submerged Last Island in Louisiana, destroying virtually every structure, including the hotels and casinos, while all crops were ruined.

Inland, heavy rainfall caused the Mermentau River to flood, destroying crops and every house in Abbeville.

The cyclone was first detected in the eastern Gulf of Mexico 125 miles (201 km) west-northwest of Key West, Florida, on August 8, 1856.

During the early evening of August 10 the northeastern edge of the eye crossed over Last Island (Official name: Isle Dernière) before making landfall a few hours later south of New Iberia, Louisiana.

The cyclone is believed to have struck southern Louisiana at peak intensity with an approximate central pressure of 934 mbar (27.6 inHg).

[2] Many Last Island vacationers hoping to escape the approaching storm were awaiting the scheduled arrival of the ship Star, which provided regular service to the mainland.

Ellis alerted Captain Abe Smith, who corrected the course and barely making headway against the winds, managed to pull into the channel behind the hotel.

Many managed to survive by sheltering in or behind overturned cisterns, which were large wooden cylindrical tanks reinforced with iron hoops.

A sturdy wooden enclosure that held large terrapins, a regional delicacy, provided enough protection to save several individuals.

[7] Presently, the area is the Isles Dernieres Barrier Islands Refuge owned and managed by the Louisiana Department of Wildlife and Fisheries to provide protected nesting grounds for pelicans and other waterbirds.

Farther east, storm surge and abnormally high tides left some sections of Plaquemines Parish inundated by several feet of water, resulting in a near-total loss of rice crops.