Ornithologists said several sightings of the bird had been made in a refuge in Arkansas state and video of the bird made last year has been released.
More than 50 experts and biologists took part in an operation to find the bird again after the initial sighting was made by a kayaker on the White River in eastern Arkansas, National Public Radio (NPR) reported.
The last time the bird was sighted was in 1944, and widespread logging in the region was blamed for its demise.
In 1971, a reported sighting in South Carolina sent environmentalists into a frenzy, with journalists dispatched to search for the bird and the state legislature banning logging in the swamp where it was sighted.
Congress later directed $50m for the creation of the state’s first national park at the Congaree Swamp.
This time, the bird’s existence is known for sure, and experts from the Cornell Laboratory of Ornithology in New York and The Nature Conservancy have kept the secret for a year to allow time to protect the bird’s habitat in the Cache River National Wildlife Refuge in Arkansas.
The Nature Conservancy and federal agencies have been buying land in the district to better protect the bird’s habitat.
The ivory-billed woodpecker is described as a large, showy bird with a red head and cream-coloured bill, and government agencies have announced a $10m package to protect it.
Private groups and individuals have already committed around the same amount to buy land and research the woodpecker’s habitat.
“This is a rare second chance to preserve through cooperative conservation what was once thought lost forever,” said Interior Secretary Gale Norton.