LOS ANGELES (CBSLA.com) — President Barack Obama is expected to declare 346,000 acres of land in the San Gabriel Mountains as a national monument.

“I am overjoyed and thrilled,” said Rep. Judy Chu, D-El Monte. “This is a historic moment for the Los Angeles area, and it has been a long time coming. The San Gabriel Mountains are a treasure, providing 70 percent of the open space for Angelenos and attracting more than 3 million visitors a year.

READ MORE: Sunday Expected To Be Busiest Travel Day Of Thanksgiving Season At LAX

Chu had proposed declaring more than 600,000 acres of the San Gabriel Mountains as a national monument, a proposal that was blasted by Republican lawmakers and critics who feared the designation amounted to a “federal land grab.”

READ MORE: No. 13 BYU Rallies From Blown Lead To Beat USC 35-31

In an apparent effort to appease critics, Obama’s executive order is expected to exclude some areas, such as Mt. Baldy and Wrightwood.

The president is scheduled to arrive in Los Angeles at 2 p.m. Thursday for a discussion on the economy and an evening fundraiser. Officials say Obama will make the announcement during an event at 12:40 p.m. Friday at Frank G. Bonelli Regional Park in San Dimas.

MORE NEWS: Suspicious Vehicle Prompts Response From SWAT, Beverly Hills Police

(©2014 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Wire services contributed to this report.)