Racing enthusiasts watched the thrilling 2-year-old champion, Sun Briar, in the spring of 1918 as she got ready to run in the Kentucky Derby. As a gifted 2-year-old, Willis Sharpe Kilmer's and Henry McDaniel's Sun Briar had many people hoping for great things from him in 1918, and taking home the Kentucky Derby appeared like a formality.

Despite his excellent performance in 1917, Sun Briar was not training well in time for the Derby, which prompted trainer Henry McDaniel to arrange the acquisition of an unidentified gelding by the name of Exterminator to act as Sun Briar's training partner.

Exterminator, a horse, bred by F. D. Knight and owned by J. C. Milam as a 2-year-old, had shown promise in 1917, winning two of his four appearances and placing fourth in the other two.

 Exterminator had never been in a stakes race, but Milam had nominated him for the Kentucky Derby and placed a high value on the colt even though he had never run in a stakes event. Exterminator, though, had impressed McDaniel, and despite the cost, the transaction was done, giving Sun Briar his coworker.

Exterminator turned out to be faster than Sun Briar, which was the main issue. And after Sun Briar's performance in the Derby was removed because of his poor training, Kilmer regretfully chose to enter Exterminator in its place.

Six years of a roller coaster ride were about to start.

He hadn't raced in nine and a half months, so he got no benefit from any preparation races. Exterminator's Kentucky Derby performance stunned the world. 

Exterminator took the lead in the Derby after six furlongs on a sloppy course, was headed with a quarter of a mile remaining, but bravely fought back to win by a length as a 29.60-1 longshot.

Exterminator demonstrated that his Derby success wasn't an anomaly by taking four other stakes contests throughout the remainder of the year, including the Pimlico Autumn Handicap.

He also showed incredible endurance, competing for five times in October and four times in November. He also preferred long-distance races when he defeated more experienced horses in the two 14-mile Latonia Cup Handicap.

He would quickly become legendary due to his toughness and tenacity.

Exterminator competed in 21 races, all in 1919, at ten different tracks in four other states, winning the Ben Ali Handicap and Camden Handicap early in the season, the one 34-mile Saratoga Cup in August, and the two 14-mile Pimlico Cup Handicap after the year. 

He defeated the talented Wildair on August 21 to win the Windsor Jockey Club Handicap, and then on August 28, he conquered that foe again in the George Hendrie Handicap.

Exterminator demonstrated his steel resolve by shipping from Windsor to Saratoga, where he won the one 34-mile Saratoga Cup on August 31 by six lengths against the champion mare Cleopatra, just three days after the George Hendrie! 

Two weeks later, at Belmont Park, he carried 128 pounds to victory in the two-mile Autumn Gold Cup, defeating Damask by a head despite giving that for 30 pounds back. 

Exterminator reduced his distance and increased his weight assignment to 132 pounds ten days after returning to Canada. Yet, he still managed to defeat My Dear, who was carrying 40 fewer pounds by a head in the one 1/4-mile Toronto Autumn Cup!

With an easy victory in the two 14-mile Ontario Jockey Club Cup under 134 pounds, Exterminator extended his winning streak to six straight contests. After losing in the Bowie Handicap, he finished the season with a narrow victory in the two 14-mile Pimlico Cup Handicap, demonstrating his complete dominance of the long-distance cup races. Exterminator was the champion handicap horse of 1920 after winning ten races, nine of which were stakes races.

Exterminator had advanced to greater heights with each racing season, and despite everything he had achieved, the greatest was yet to come. Exterminator, now six years old, began 1921 slowly but warmed up in August, winning the Merchants & Citizens Handicap at Saratoga by a length and the one 34-mile Saratoga Cup in a walkover since no horse could be found to compete against him at his preferred distance. 

After winning the Autumn Gold Cup by six lengths while weighing less than 130 pounds, he and My Dear put on a show in the Toronto Autumn Cup for the second time in a row, with Exterminator carrying 137 pounds and winning by six lengths.

Later, he added a third consecutive Pimlico Cup Handicap to his resume, reclaiming the title of champion handicap horse.

Nobody informed Exterminator that it had been four years since he had won the Kentucky Derby because he went on to surpass all expectations in 1922. 

Exterminator, a 7-year-old sprinter, won the Harford Handicap by a length against the best sprinter, Billy Kelly, by cutting back to six furlongs to start the year. 

He won the one 1/16-mile Pimlico Spring Handicap in his second race by a head while carrying 133 and 138 pounds, respectively. He then won the Clark Handicap and Kentucky Handicap easily, taking 133 and 138 pounds, respectively. 

He won his subsequent outings in short handicap races that acted as warm-ups for the one 1/8-mile Brooklyn Handicap, where he would face off against Grey Lag.

Grey Lag was incredibly gifted and the most talented horse Exterminator has ever encountered. With ten victories from 14 starts as a 3-year-old in 1921, including the Belmont Stakes and Brooklyn Handicap, Grey Lag dethroned Exterminator as Horse of the Year. Given his skill, Grey Lag was a solid favourite for beat Exterminator in the 1922 Brooklyn Handicap. He would also carry nine fewer pounds than Exterminator, making his mission more straightforward.

Old Bones, though, wasn't prepared to vacate the stage. Grey Lag adhered to the plot exactly, keeping pace with Exterminator at all times and taking the lead into the last stretch, but Exterminator then took centre stage and changed the conclusion. Exterminator engaged Grey Lag with a furlong remaining, refused to back down when Grey Lag retaliated, and eventually reeled in his younger foe to win by a head as the racing world watched in awe.

Undoubtedly, that was the best race of his career.

To finally claim the title of Horse of the Year that year, Exterminator would triumph in three additional stakes contests, including the Saratoga Cup and Toronto Autumn Cup. He won the Philadelphia Handicap under 129 pounds during a condensed 1923 season but was disabled with an ailment after just three starts.

 As old age finally caught up to him, he failed to win a stakes race the following year, his final season of competition. However, he did succeed in winning three allowance races, and he finished fourth by 1 12 lengths in the Coffroth Handicap, which had a $51,000 purse and was the most lucrative horse race ever run.

With a third-place performance in the Queen's Hotel Handicap at Dorval Park in Canada, Exterminator put an end to his illustrious career. 

Old Bones retired to Kilmer's farm, Remlik Hall, where he lived happily ever after until he was 30, surrounded by his adoring fans.

Fun facts

Due to Exterminator's somewhat skeletal appearance, he was known as "Old Bones."

Exterminator was trained by eight different trainers and ridden by 18 other jockeys during his career.

With a formal record of 50 victories, 17 seconds, and 17 thirds from 100 races and earnings of $252,996, Exterminator retired.

Exterminator was a retired man who insisted on travelling with his pony, Peanuts—there were three of them over the years.

Exterminators are shown tremendous adaptability by winning races from 5.5 to 18 furlongs, which is highly uncommon.

Additionally, he prevailed on fast, sound, heavy, muddy, and sluggish tracks.

In 36 races, Exterminator carried 130 pounds or more, including ten straight in 1922. During that run, he won the Kentucky Handicap by successfully taking 138 pounds, and in the Independence Handicap, he attempted to carry 140 pounds but came in sixth.