Interior Secretary Ryan Zinke and Oregon Gov. Kate Brown will both visit the Cascade-Siskiyou National Monument this weekend, spurred by Zinke's review to determine whether January's expansion of the monument was appropriate under the federal Antiquities Act.

The Interior Department announced Friday morning that Zinke will visit Saturday but gave no other details of his trip to view the 113,013-acre monument, which is primarily in southeastern Jackson County but now stretches west into Klamath County and south into California after President Barack Obama's expansion just before leaving office in January.

Brown's office announced Friday afternoon that she will tour the monument Sunday on horseback with monument supporter Dave Willis of the Soda Mountain Wilderness Council before meeting with Zinke and local elected officials later that day.

A monument expansion supporter, Brown said in a statement that Oregonians must defend existing public lands and the "special wonders" within monuments for the future.

"Oregonians have a long tradition of environmental stewardship and deep appreciation for our public lands, and I will make sure the voices of Oregonians are heard by Secretary Zinke and the federal administration,” Brown said in the statement.

Local players in the monument debate say they also have meetings scheduled with Zinke to make their cases directly to the man tapped by President Donald Trump to determine whether expansion of this and 26 other monuments fit a series of litmus tests and then recommend what, if any, federal action should take place.

The monuments were all created by presidential decree as spelled out in the Antiquities Act, which allows presidents to designate monuments without public comment.

The Antiquities Act provides no language for presidents to remove monument designation, and no president has attempted to do so under the 101-year-old act. Congress, however, can vote to alter monument boundaries.

Willis, who has argued that the monument expansion should have been larger based on scientists' recommendations that more highlands and stream headwaters need protection, confirmed he and other supporters will have a 30-minute meeting with Zinke. But Willis declined to say when or where that meeting will be, other than it will take place in Medford.

"This monument and so many other monuments have been such a gift to present and future generations that it's strange that any president would want to take those gifts away or diminish them in any way," Willis said.

Jackson County Commissioner Colleen Roberts, a vocal opponent of the monument's expansion and part of a suit challenging the legality of adding O&C Act lands in that expansion, did not immediately return telephone calls seeking comment.

Last Monday, Oregon Attorney General Ellen Rosenblum sent Zinke a letter stating her office would take "appropriate legal action" should the Cascade-Siskiyou National Monument be reduced in size.

The public comment period on the issue ended Monday, with more than 1.2 million comments collected by the Interior Department online and thousands more via traditional mail, the agency reported.

The review is looking specifically into whether the monument lands are the smallest necessary to protect the land or objects they are designed to protect, whether the lands are appropriately classified as of historic or scientific interest, and their impact on multiple-use.

The review also includes looking into the economic impacts of monument status and whether the federal government can properly manage those lands, according to an agency release.

Zinke said in a statement Tuesday that if lands are removed from monument status, they would remain in federal ownership and not sold.

The original 66,000-acre Cascade-Siskiyou National Monument was designated by President Bill Clinton to protect what he called its "spectacular biological diversity." A 2015 scientific study recommended a larger expansion than Obama signed to ensure that biodiversity is protected, especially when considering the threats of climate change.

The monument now includes 113,013 acres in a footprint that covers about 137,500 acres. Private lands, including more than 2,000 acres of Murphy timberland, inside that footprint remain private and are not subject to monument rules, which ban commercial timber harvest but would allow well-vetted noncommercial cutting.

Announced in April, the original review targeted 27 monuments, but Zinke announced Tuesday that he would recommend two monuments not be altered — Craters of the Moon National Monument in Idaho and Hanford Reach National Monument in Washington.

— Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or mfreeman@mailtfribune.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.