From the web page:

Henry W. Kellogg purchased the hardware business belonging to C.W. Avery in 1887. Henry operated the business as H.W. Kellogg until 1895 when he formed a partnership with his brother-in-law, Lewis Elliott, who had an established lumber and coal business. The business became known as Kellogg & Elliott.

As the nineteenth century drew to a close the entire village of Katonah prepared to move to a new site. New York City was damming the Muscoot River on whose banks Katonah was settled. Henry purchased the land on which the present Store stands in the late 1880’s, the building was built in 1900.

Business commenced in the new building by 1902, once again under the name of H.W. Kellogg: the partnership to the Coal and Lumber Business had ended. Henry and his family lived in the spacious second floor apartment.

The first US Post Office in the new village occupied the northwest corner of the building alongside the Hardware Store. Henry Kellogg was Katonah’s Postmaster for about 10 years. The basement, and later the barns and sheds, housed the burgeoning plumbing, heating and sheet metal shops. The original barn housed the horses and wagons used by the mechanics. There was also storage for non-perishable merchandise.

When Henry bought his business he inherited two mechanics, Thomas Smith, a Tinnier, who was great at repairing milk cans; and James Mayne, a Plumber and Civil War Veteran. As it happens, James Mayne was father to Harry Mayne, who purchased the lumber, coal and feed business from Henry Kellogg's brother in law and former partner, Lewis Elliott.