Members of the Ku Klux Klan are suspected, but the identities of thsoe responsible have eluded authorities for 40 years, The Clarion Ledger in Jackson, Miss., reported Tuesday.
Offering the reward is the Mississippi Religious Leadership Conference, a multiracial, ecumenical group formed in the aftermath of the killings.
"We're hoping this reward will cause someone to bring forward information to the attorney general that will lead to the arrest and conviction of individuals," said the Rev. Paul Jones, executive director of the conference.
People with information on the slayings are being asked to call the state attorney general's office.
Attorney General Jim Hood said his office intends to complete its investigation by the end of January.
A grand jury would then consider the first indictments in the deaths of Michael Schwerner, James Chaney and Andrew Goodman.