Pepper was born on a farm in Davis County, Iowa.[1] He attended public schools and graduated from Southern Iowa Normal School at Bloomfield in 1897. He later served as principal of the Atalissa, Iowa High School and of the Washington School at Muscatine, Iowa.
In 1910, Pepper ran as a Democrat for an open seat in the U.S. House to represent Iowa's 2nd congressional district. He won the Democratic nomination, then defeated Republican Charles Grilk in the general election.[1] He was then re-elected two years later with "little opposition."[1]
On December 22, 1913, part way through his second term, Pepper died following an operation for infection of the gall bladder.[2] He was recovering in Clinton County, Iowa, from typhoid fever, which had left him in a weakened state.[2]
In the Sixty-third Congresses, he served as chairman of the Committee on Expenditures in the Post Office Department. He also served as a member of the House Committee on Military Affairs.[1] At the time of his death, he served as secretary of the Democratic National Congressional Committee.[3] In all, he served from March 4, 1911 until his death.
Pepper had planned to enter the contest in Iowa for the U.S. Senate seat held by Albert B. Cummins, in what would be Iowa's first direct election of a U.S. Senator.[2]
He was interred in Shaul Cemetery, near Ottumwa, Iowa.
"The lone duck in the brood," Jay "Ding" Darling editorial cartoon regarding Iowa's election of one Democrat (Pepper) to Congress in 1910, Iowa Digital Library.