Ranch names do NOT change names when passed down, nor do ranch names necessarily change names when sold. I've known one large ranch that is in the third generation, same name. The Circle C appears to have kept name intact through generations. It appears to be going into piece meal lots now... Ah, such is life in the "new" west.
"The original Circle C Ranch was homesteaded in the Meadows Valley in the early 1800s by the Campbell family. The large ranch spanned from Meadows Valley to the Snake River in central Idaho. The Idaho Historical Society has more information about the Circle C Ranch."
"Founded in 1884 by Charles A. Campbell. C.A. Campbell resided in Meadows, ID, 51 years. Died in Boise, April 16, 1932. Mr. Campbell and sons were well known stockmen, owners of the Circle C ranch. He is survived by five children.
I did find many references in the Idaho Historical Society listings to the Circle C Ranch in numerous collections. Some just by association (the ranch name in sales or commentary, etc). But, none identified the surname of "Herd/Hurd."
Ownership had gone down to Rollie Campbell and Margurite Allen Campbell, mid 20th Century:http://idahohistory.cdmhost.com/cdm4/item_viewer.php?CISOROO...
From a book, re: the cattle Industry written in 1946:
"The Circle C Ranch own the biggest herd of cattle in the valley at present, and have for a long time. They also own more land in the valley than anyone at present."
The name "Circle C" was also "probably" their cattle brand name (An iron heated in a fire to brand cattle). When a property/brand changes names, a transfer of that brand is completed. The State Brand Inspector's office would have a listing of the current owner; but possibly also the transfer list. I have seen Brand books (books with photo's of brands), but can't find one online. These people should have the data and possibly information about the owners: http://www.isp.idaho.gov/brands/index.html
Enough background, I'm sure you can find, or have found enough information on the ranch itself and/or the Campbell family.
The Herd/Hurd family:
I see you've only posted 26 inquiries on the Rootsweb message board system, at least using this user name. When you post, it is important to fully identify the people you seek. In this case, their full date of birth is especially helpful. If you don't have that, an approximate DOB, with the place of birth, parents, siblings, date of death, etc, is helpful. It is far easier to track a person than to begin at a specific location, especially if family lore is the heart of the knowledge.
In one of your other postings, you identified "Roe" and "Lum" Herd/Hurd, and they were from Hancock County, TN. They may have worked for Luther Gillenwater, then returned to TN. You also identified "Roe" was in reality: James Monroe Hurd/Herd. THAT helps in locating someone. Knowing their "REAL" name is more helpful than any nickname.
Now, with THAT information, I was able to find a family tree on the Hurd family:http://trees.ancestry.com/tree/6883078/person/-1210219161?ss...
It is owned by a Sandy Marting. I sent a message to this person to read this thread and help you if possible. You can access this tree if you have an Ancestry membership, or you can access it at your local library using your library card on their computer system, "IF" they have the library version of Ancestry. Many do.
This tree shows James Monroe Hurd, was born 1 Jan 1880, died about 1941.
His brother, Christopher Columbus (Lum) Hurd, was born 11 Feb 1882 in Hancock County, TN, and died August 1971 in Hancock Co, TN. He married Causby Wright Templeton in 1902. They were both sons of Elbert L. Hurd and Nancy Clementine Anderson. This family tree showed many children of Elbert and Nancy, but did not show a George Hurd. Other sons were "America Hurd," "Joseph Hurd," "App Hurd," "Alexander Hamilton Hurd," and "John Davis Hurd."
The 1900 Census for Hancock County, TN
Both Christopher C, and James M. Hurd were living at home with parents Elbert and Nancy, along with their siblings. This census was enumerated on 11 June 1900.
The 1910 Census for Hancock Co, TN
James M. Hurd was living with his wife Dara(?), age 23 and son Ray. He had been married 4 years. Dara had 3 children/2 were living.
The 1910 Census for Boise, Ada County, Idaho
Luther Gillenwater, age 45, born in Tennessee, employed in livestock/sheep rancher. He was living with his wife, son Harry, Mother-in-law Ellen, age 64, and had three lodgers living in the home. He was living in town at 1113 Franklin Street. Because of this residence, he may or may not have had his own ranch, with his own stock. Although the census record said his employment was on his own account. Luther died in Boise in 1945.
As far as a George Hurd, I find a George Hurd in the 1910 Census of Hancock County. He was age 22 (born about 1887/1888), son of Wallen T. Hurd, a widower. This George Hurd would have been to young in 1900 (as found in the 1900 Census) to have been in Idaho at that time, age about 12. This George had brothers "Jackson" and "Huston," and a sister "Easter." If this is not the correct one, there were 210 George Hurds in the census of 1910, a few others born in Tennessee, but not in Hancock, TN; or in Idaho.
As far as any of the Hurd family working in Idaho on a ranch or with someone working on a ranch. There would be very little, if ANY, records. Cattle ranchers had a lot of short term workers, drifters, cowboys, etc. There "might" be local records in the Idaho Historical Society collections of others, but these would just be notes of payments or other business transactions. These ranch workers sometimes lived on the ranch in bunk houses, sometimes in town.