The family home was a small log house on Sandusky Street in Zanesfield. Earl's father was a harness maker, who served as a pioneer veterinary surgeon for central Ohio, and he bought and sold horses for the army during the Civil War. He had a certain ability with horses and spent as much time caring for animals as he did in mending saddles. From a formula reportedly given to him by the Indians (though this is uncertain), Andrew made a strong-smelling brown concoction that was applied to horses' shoulders when they stiffened from the spring ploughing. The formula grew to be in great demand in the area.
Andrew Sloan pursued his skill with healing animals until he was a self-taught veterinarian, becoming known as the "Village Vet" and "Doc Sloan." A notice that appeared in the Logan County Gazette on September 6, 1856 advertised:
Dr. Andrew Sloan takes this method of informing his old friends, who have so liberally patronized him for many years, that he is now prepared to practice as a Veterinary Surgeon, and will attend to any call in his profession in Logan and adjoining counties. Dr. S. professes to cure Poll Evil, Spavin, Splints, Curb, Callous, Sweney, Shoulder-jam, or any other disease, external or internal. So bring on your cripples. Residence at Zanesfield.
N.B. Dr Sloan is prepared to furnish stable or pasture for horses from a distance. Medicines of all sorts furnished, and prescriptions given. - Charges reasonable.
Earl attended school in Zanesfield's old school building, directly across the street from his home. He did not attend more than the elementary grades, but did learn to read and developed a great appreciation for books.
Townspeople recalled that Earl was mischievous as a youth and objected to the nickname "Spider" that was attached to him for reasons unknown.
Under the tutelage of Frank Pope, Earl also became a harness-maker, beginning his apprenticeship at the age of fifteen.
At some point in the brothers' venture, someone applied the liniment to his back, discovering that it relieved his own discomfort, as well. Thereafter, the Sloan brothers began selling even more of the liniment advertising it as "good for man and beast".
Earl risked the money necessary for advertisements in Chicago's streetcars, and in time, the orders for the liniment multiplied.
In 1900, Foreman Sloan left the business, but Earl continued, adopting his father's title "Doctor" and organizing a company to manufacture the liniment. The company offices were moved to Boston in 1904 when Dr. Sloan purchased a large factory building, formerly owned by Green's Nervura Medicine Company. On October 26 of that same year, the business was incorporated as "Dr. Earl S. Sloan, Incorporated." Records in the office of the Secretary of State for the Commonwealth of Massachusetts disclose that the authorized capital for the new corporation consists of $50,000, $10 per parcel. The principals of the new corporation were Dr. Sloan, Archie MacKeigan, and Andrew Sloan, who served as the Treasurer. A business report of the time indicated that "the concern is recorded as one of the largest of its kind and goods are sold extensively throughout the country."
Dr. Sloan's business grew rapidly due to his advertising efforts. He was particularly fond of newspaper advertising. Dr. Sloan's promotional efforts included frequent travel. A newspaper article from 1907 announced that he had completed arrangements for an extended trip through Great Britain and Europe during the summer months of that year.
Dr. and Mrs. Sloan made their home at Pine Lodge in Roxbury, Massachusetts. It was purchased in 1909 and included nine acres, located on the east side of Cottage Avenue. In all, the house included twelve rooms, three baths, and nine fireplaces, and was luxuriantly furnished.