Deer Island, in the Columbia River, was named by Lewis and Clark. They first visited the island on November 5, 1805, on their way down the Columbia and again on March 28, 1806, on their return. It was on the second visit that the party had good luck getting venison. Captain Lewis noted in his diary that the Indian name for the island was E-lal-Iar, or Deer Island. The compiler is unable to identify this Indian word. The town of Deer Island, which is on the mainland, was named for the island. The post office was established in 1887.