The vote gives the landmark important legal protections -- Harris County, which owns the building, will have to seek approval from the state before making any significant structural changes to the building.
Last September, Harris County Commissioners agreed to a $105 million plan to revitalize the aging building, including installing two levels of underground parking.
PHOTOS: Astrodome revitalization plan
History of the Astrodome
On January 31, 1961, Harris County voters approved a general bond issue of $22 million to build the Astrodome. About a year later, ground was broken for the new stadium. Voters had to dip into their pockets one more time and approve another $9 million in bonds to complete the project.
The total price tag for the dome was $20 million, but the overall project, including streets, bridges and storms sewers was $40 million.
Click here for more about the Astrodome's history.