Lake County Discovery Museum County Historian & Collections Coordinator Diana Dretske reports that the two men are Samuel Miller and Issac Winter.  Miller's father, Jacob Miller, "established a mill on Mill Creek (southern Newport Twp) in 1835," according to Dretske (email May 2, 2012).  Isaac Miller "conducted the saw mill at this location."  Dretske reports that "C. T. Heydecker of Waukegan placed the boulder at the mill site and painted the date 1835 on it to mark the establishment of the mill."  the present existence and/or whereabouts currently are being pursued.  

This photograph, by Waukegan photographer R. W. Hook, records one of the earlier local commemorative efforts to mark an historic site in Lake County, and its later note by Getz alludes also a similar activity a year earlier.  This photo is an early, historic record of the beginnings of recording acrtivties relating to county history.  The Getz layer of identification also refers to another earlier period of historic information collecting in Lake County, IL. Thus, this artifact of an occasion commemorating an historic landmark over a century ago bears inidcations of early and mid-20th c. stewardship of such materials in the semi-private hands of the informal, by today's standards, Lake County Historical Society under Mrs. Dunn and Mr. Getz.

Transcription of handwritten caption on the verso of the image:

in ink:

"This picture dated Aug. 1910,

according to Mrs. Dunn, is of

a large boulder located in

Newport Township on the

grounds of the Hunt Club.

             J. R. G."

in pencil, to the left of the initials at the bottom:

"see other picture of

rock on wagon"

Mrs. Dunn was Bess Bower Dunn (1877-1959), for whom an excellent, illustrated biography has been provided by Diana Dretske of the Lake Co. Discovery Museum, on her blog: http://lakecountyhistory.blogspot.com/2011/01/bess-bower-dunn-1877-1959.html

The "Hunt Club" originated west of Lake Forest ca. 1900 for fox hunting English style (Onwentsia Hunt) but in 1928 moved to northwest of Waukegan, near rural Milburn and Wadsworth, when land west of Lake Forest began to be built up in the 1920s. Though this was after the 1910 photo, it was active in the 1950s when Mr. Getz likely took possession of the photo from Mrs. Dunn. The hunt club's territory is remembered best with Hunt Club Road, and the boulder may or may not have been near that thoroughfare within the larger range of the hunt countryside.  

The reference to the "other picture of rock on wagon" alludes most likely to "the large boulder that was removed from the Sheldon property (today St. Mary's of the Lake) and used to commemorate Daniel Wright," an earliest settler in the county, according to Dretske.  It was placed "on route 21 (Milwaukee Avenue) in Half Day (present day Lincolnshire) in 1909," and about whom there is more on another of Diana Dretske's blog posts, http://lakecountyhistory.blogspot.com/2009/09/daniel-wright-countys-first-settler.html.  Photos there show Wright, that second menitoned rock in its original and in its post-1996 locations.  

Jame R. Getz, a long-time resident and mayor of Mettawa, Lake County, and who died in the mid 1980s, followed Mrs. Dunn as president of the Lake County Historical Society, the County's first such organization.  This effort has been succeeded by the County Discovery Museum and by the many fine local museums and societies in Lake Forest, Waukegan, etc.  Mr. Getz left his historical papers, etc. to Special Collections. He was a 1950s library committee member and later trustee of Lake Forest College. 

Diana Dretske reports by email (May 3, 2012) that the the Museum also has a copy of the photo, in the Browe School History (2003.0.36).