The group sent a letter to the President urging him to extend protection to 1.7 million acres around the Grand Canyon.
President Obama has created 23 monuments using his power under the Antiquities Act, and has indicated a willingness to add the Grand Canyon.
Yuma pastor Victor Venalonzo of Iglesia Bethania Church is part of the faith-based alliance in support of the proposal. He said the group has been active in educating communities about the region.
"So we can leave a legacy for our grandchildren," Venalonzo said. "Lately we have seen alot of abuse on the waters, on the environment that god created to protect."
A new monument will permanently ban new uranium mining in the park’s watershed.
Republican Senators John McCain and Jeff Flake of Arizona both oppose the new monument.
They've also sent a letter to President Obama saying the designation would restrict access and management options in hunting, livestock, wildfire prevention, mining, and other forms of outdoor recreation and tourism.