The winner of the 1880 Kentucky Derby was Fonso, a chestnut colt bred by A. J. Alexander of Kentucky's Woodburn Farm.1

Fonso could trace his heritage back to the Darley Arabian, but was more recently the son of King Alfonso, a grandson of Vandal (a line that also produced Vagrant and Fonso's half-brother, Grenada, winner of the 1880 Preakness and Belmont ).6

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          |              |                     | King Tom by Harkaway  
          |              | Phaeton             |                          
          |              |                     | Merry Sunshine     
          | King Alfonso |                     |                            
          |              |                     | Vandal       
          |              | Capitola            |                           
          |              |                     | Mare by Margrave
Fonso -----------------------------------------------------------------  
          |              |                     | Sheet Anchor          
          |              | Weatherbit          |
          |              |                     | Miss Letty
          | Weatherwitch |                     | 
          |              |                     | Birdcatcher   
          |              | Mare by Birdcatcher |     
          |              |                     | Colocynth     
-------------------------------------------------------------------------    

Fonso was born in 1877. His owner, John Snell Shawhan, was a third-generation Scotch-Irish-American who operated his grandfather's distillery at Shawhan Station, Harrison County, Kentucky. Shawhan was a lifelong bachelor, but his hobbies included owning fine race horses.2

As a two-year-old, Fonso won the Maiden Stakes and the Colt Stakes.3 His early performance made Fonso a contender in the three-year-old stakes circuit the following year. Fonso was trained by Tice Hutsell (who married one of Shawhan's cousins, Ada Minerva Shawhan) and ridden by the African-American jockey George Lewis.

May 18, 1880, the day of the sixth Kentucky Derby, was dry and clear with low and high temperatures of 62 and 87 degrees F in Louisville.4 The track at Churchill Downs was fast but dusty. Five horses were entered in the race in which Fonso carried 105 pounds. Lindsey Taylor, a reporter for a Lexington newspaper, later described the running of the Derby:

Fonso broke in front at the gate and led all the way to win by a length. A foul, claimed by the jockey of the runner-up horse, was not allowed. The track was extremely dry and the dust kicked up by Fonso practically obscured the nearest pursuers.2

Fonso posted a time of 2:37.50 on his way to winning $3800. The order of the other finishers was Kimball, Bancroft, Boulevard, and Quito.5

In his career, Fonso won five of twelve total starts (including the Phoenix Stakes), finished second three times, and was third twice. When his owner died in 1886, Fonso became the property of Shawhan's sister, Anna Kimbrough (Mrs. Sterling Price Moore of Shawhan Station) but was later bought by Henry Clay McDowell of Lexington and stood at stud on his farm, Ashland.2

Notes:
1. http://tcm.bloodhorse.com
2. http://homepages.rootsweb.com/~shawhan/volumeone/240-265.pdf
3. http://www.fortunecity.com/marina/commodity/1881/files1.html
4. http://www.crh.noaa.gov/lmk/climate/derby.txt
5. http://www.thoroughbredchampions.com/library/kyderby.htm
6. Chew, Peter, The Kentucky Derby: The First 100 Years, Houghton Mifflin Co., Boston, 1974.