John Lawrence Sullivan (October 15, 1858 – February 2, 1918) is widely recognized[attribution needed] as boxing's first modern world heavyweight champion[citation needed].

He was born in Roxbury, Massachusetts (now a part of Boston) to Irish emigrant parents, Michael Sullivan from Abbeydorney, County Kerry and the former Catherine Kelly from Athlone, County Westmeath. Sullivan was nicknamed The Boston Strongboy. As a youth he was arrested several times for participating in bouts where the sport was outlawed, and he went on exhibition tours offering people money to fight him. In 1879, he challenged anyone in America to fight him for $500.

In 1883 - 1884 Sullivan went on a coast-to-coast tour by train with five other boxers. It was scheduled to comprise 195 performances in 136 different cities and towns over 238 days. To help promote the tour, Sullivan announced that he would box anyone at any time during the tour under the Queensberry Rules for $250. It has been claimed he knocked out about 30 men during the tour, but there is no proof to back this claim.
Source : Wikipedia