Daniel Lucius "Doc" Adams (November 1, 1814 – January 3, 1899) was an American baseball player and executive who is regarded by historians as an important figure in the sport's early years.

In addition to his playing career, Adams manufactured baseballs and oversaw bat production; he also occasionally acted as an umpire.

After being schooled at Kimball Union Academy in New Hampshire from 1826 to 1828 and Amherst, Massachusetts' Mount Pleasant Classical Institution, Adams attended three colleges from 1831 to 1838.

[5][6] Nancy Adams, Daniel's sister, indicated in a letter penned in the early 1830s that he began playing with "bats and balls" by this time.

In an 1896 interview in The Sporting News, Adams said that "soon after going to New York I began to play base ball just for exercise, with a number of other young medical men.

In an inter-squad game held that day, which was the Knickerbockers' last of the year, Adams scored nine runs for his team as they defeated a side picked by William R. Wheaton, 51–42.

Playing three times at shortstop and once at first base defensively, he contributed 12 runs offensively, including a six-run effort in the Knickerbockers' 37–23 victory over the Empire club on June 24.

[28] As a player, Adams created the concept of the shortstop position, according to Thorn and Baseball Hall of Fame researcher Freddy Berowski.

[32] Adams hit left-handed; he said that his batted balls occasionally went into a river by the Elysian Fields, the ground in Hoboken, New Jersey, where the Knickerbockers practiced and played.

[14][36] According to author Peter Morris, Adams' ball-manufacturing efforts helped to keep the Knickerbockers in operation during their first few years, as they would otherwise have had difficulty finding balls.

[10] One notable example was the final contest of a three-game series between all-star teams from Brooklyn and New York City, held on September 10, 1858, in Long Island.

During the game, which the New York City all-stars won 29–18, Adams became the first umpire to use a new rule allowing for a strike to be called against a batter who refused to swing when "good pitches" were thrown to them.

[47] The Eagle Base Ball Club, desiring a unified set of rules, sent a message to the Knickerbockers requesting that a committee be formed.

[48] After again being named a director in 1855, Adams became president of the Knickerbockers for the fourth time, winning an election held at the club's April 5, 1856, meeting.

[53] A two-man committee was created with the aim of working with the Eagle and Washington clubs to resolve the debate over how many players to field in official games.

A convention was scheduled for early 1857, and Adams joined a three-man committee tasked with encouraging local clubs to send delegates.

[57] He authored the initial draft of the regulations with what The New York Times' Richard Sandomir called "an upright script and strong hand.

[59] Fellow Knickerbocker William H. Grenelle copied Adams' work onto blue pages, and modifications and notations were made as the convention progressed.

Among other changes, part of the rule Adams had written on game length was crossed out; the number nine was replaced with seven, before the motion that settled the issue was introduced.

[60] In May 1857, Adams presided over a player convention where nine-inning games were officially made part of the rules of baseball for participating teams.

[69] Despite his support for the fly rule, in 1858 Adams successfully motioned for NABBP regulations, including outs on bounces, to apply to the Knickerbockers.

Shortly after his motion, he organized a Knickerbockers meeting to discuss the fly rule and "obtain a reconsideration" of the newly passed resolution.

At the meeting, the Knickerbockers decided to exclude outs on bounces from their practice games and contests against teams that supported the fly rule.

[75] Adams continued to maintain his medical practice during his baseball career, but was forced to abandon it in 1865 after he began suffering health issues.

However, by the time conventions led by Adams had enacted those rules in the late 1850s, Cartwright had traveled to California and was no longer a member of the Knickerbockers.

[30][80] Adams is said to have avoided "campaigning for credit" for rules changes after he left the Knickerbockers; researcher Gary O'Maxfield said of him that he "didn't like to brag.

Dickey Pearce was the first player to field in that area, and his ability to prevent base hits in the formerly unoccupied territory convinced other teams to employ similar tactics.

[7][8][83] After the Doubleday reports in 1980, The New York Times received a letter from the great-great-grandson of Adams that the Courant said attempted "to try to set the record straight.

[11] Mont Vernon holds an annual baseball game in honor of Adams, which incorporates the rules of his era, as a part of the town's Lamson Farm Day.

[87] While Adams' contributions had received notice from historians, Associated Press writer Andrew Dalton called such reports "somewhat speculative" in nature before 2016.