Crews are covering the world-famous Hollywood sign with panels reading 'Save the Peak'.
It's part of a campaign by a nature preservation group to save an adjacent hilltop from development.
Trust For Public Land spokesman Tim Ahern said the letters will be covered until Tuesday. The group has raised about $7m of the roughly $12m needed to buy the Cahuenga Peak property from its current owners, who have announced plans to develop the 138-acre parcel into luxury homes.
The Hollywood letters were altered in 1992 to promote the film Cool World: then, some residents were angered because they feared the giant Kim Basinger likeness seated on the D would draw crowds to their neighbourhood.