Ross Barnes (1850-1915) was the dominant hitter of his era, winning three batting titles and leading the league three times in on-base percentage and slugging percentage. He also led in runs and hits four times, thrice in doubles, twice in bases on balls, and once each in triples and stolen bases. He led his team, the Boston Red Stockings to four of the five National Association pennants, only losing in 1871 to Levi Meyerle's Philadelphia Athletics.
His next stop was to the brand new National League's Chicago White Stockings, where he moved with star teammates Cal McVey and Al Spalding. Led by Barnes, McVey, Spalding and a young third baseman by the name of Cap Anson the Stockings won the NL's first pennant in 1876. He led the league in batting with a .429 mark.
This would be the star second baseman's last good year. In 1877 the National League would rule illegal the hits he had used to make himself one of the league's best batters. Known as "fair-foul" hits, he exploited the rules of the time, which ruled that any ball that first land fair are in play, even if they end up in foul territory. Ballparks of the time had lots of foul territory, so he would often end up with a double or triple while the defense tracked the ball down. He played three more years in three different cities after the rule change, never hitting above .270.
Sources: www.baseballreference.com, www.baseballlibrary.com