The original architect for 901 E. Rosemary Rd. is Lawrence Gustav Hallberg (1844-1915). 

A resource mentioning the architect is a Chicago Tribune notice, Nov. 11, 1888, of work on the 901 E. Rosemary Rd. house’s beginning for Levi Yaggy, a Chicago educational pubnlisher, is found on p. 28 (col. 3, third new paragraph). Begun in late 1888, the house would have been occupied by 1890.

Lawrence G. Hallberg (September 4, 1844 to December 4, 1915) was born and educated in Sweden (Polytechnical School, Gothenburg), traveled in Europe, and began work in the London office of Sir Digby Wyatt.  He came to Chicago in 1877 (or 1871, according to obit. in Am. Contractor, Dec. 11, 1915, 67), organizing L. G. Hallberg & Son in time.   He was a fellow of the Am. Institute of Architects.  Hallberg was an early pioneer in concrete construction. 

Special Collections also has the original 1890s record book of the Lake Forest Water Co., showing that by 1893 (the service started in 1892) Levi Yaggy was a customer, though he must have had a well by 1890.  See: http://collections.lakeforest.edu/archive/files/aa0c4da243f1bb5a5b5de08e4fac8e1d.pdf  Here too is more general information on the water co.: https://www.lakeforest.edu/library/archives/indexes/lfwatercocustomerbk.php As p. 75 of the water co. book shows, there was a place to house the horse and two additional animals, with watering, apparently the Linville house today, to the southwest.  But no separate water closet there, only one in the house.  The fellow who took care of the animals may have lived in a room in the house, and maids handled chamber pots, etc.  Or he could have lived elsewhere.  But there must have been others.  

In the Chicago Tribune for June 15, 1890 it shows that Levi Yaggy had sold property on Lake Shore Dr., Chicago, south of Division St.  Maybe that was when he moved out to LF.

The house was in a Richardsonian Romanesque style like that of Henry Ives Cobb, and I always assumed that the garage was by Cobb, around the time he was working on the Gymnasium at the College, 1890-91—the same towers.  And it’s not impossible that the job went form Hallberg to Cobb later….    

A son, Arthur Yaggy, later attended Lake Forest University and married a daughter of Calvin Durand, one of the big college-support families.  

There's probably more on the architect at the AIA, Washington, and more on the web.  This note only just scratches the surface.  

Records elsewhere seem to indicate that Arthur Heun, architect for J. Ogden Armour’s Mellody Farm, 1904-10, renovated the house prior to 1914, and by 1920 the house was that of Lolita Armour Mitchell (Mrs. William, Jr.). The house as remodeled is shown in Lake Forest: Art and History Edition (1916): http://archive.org/stream/lakeforest00amer#page/22/mode/2up/search/lindley . the renovation consisted in part in converting the Romanesque tower into a tudor gable end and cov ering the brick facade with Befored (Indiana) gray limestone, with similar related interior alterations.

by the 1920s this was the home of William and Ginevra King Mitchell, Jr. and there was a notable robbery here ca. 1930, cited in Arpee's lake forest history (1964).     

 Levi W. Yaggy was as entrepreneurial educational publisher, by the late 1`880s headquartered at Chcagio and by 1890 living in Lake Forest. A good description of his career is found at this site: http://www.bostonraremaps.com/catalogues/BRM1182.HTM .

The photo itself was derived indirectly from descendant sources, conveyed to Special Colelctions by the current owners of the 1890 garage property, the Linvilles.