According to Peter Morris's A Game of Inches, the first known instance of an intentional walk was discovered by researcher Greg Rhodes. It occurred on June 27, 1870, in a game between the Cincinnati Red Stockings and the Olympics of Washington: "The pitcher of the Olympics did his best to let George Wright take his first every time on called balls, as he preferred that to George's style of hitting. George went to first twice on called balls, but on three or four other occasions he managed to strike the ball."
A walk is only considered intentional if the catcher gives a clear sign that he is calling for an unhittable ball. Normally he does this by standing up instead of crouching and reaching one hand outside. The pitcher then throws the ball toward the catcher's hand, and the catcher steps over to catch the ball. The catcher must be careful not to step over to catch the pitch until after the pitcher has thrown; stepping out of his box prematurely will result in a balk. If a pitcher throws only unhittable pitches without a prior signal, in the hope that the hitter will take the bait and swing on a bad pitch outside the strike zone, it is not counted as an intentional walk but as a regular base on balls.
For decades, the pitcher had to actually go through the motions of throwing four pitches outside of the strike zone; he could not simply indicate that he was conceding the base to the batter. This distinction was not normally important, but on rare occasions the pitcher would accidentally throw a hittable pitch that the batter swung at, or a wild pitch. However, in 2014, Major League Baseball introduced the "automatic intentional walk" on a test basis in the Arizona Fall League, as part of a set of measures to speed up the flow of the game; in this scenario, the manager signaled the home plate umpire by showing four fingers, after which the batter automatically moved to first base without the need to throw any pitches. In 2017, Major League Baseball adopted a variation of this rule through which the defensive team's manager simply had to signal his intention to the home plate umpire to walk the batter intentionally in order for the batter to proceed directly to first base, without the need to make any pitches. This was nominally done to speed up the game, although observers pointed out that intentional walks were so few, and were usually dispatched so quickly, that the gain in time would be microscopic. The first time the new rule was used came on April 2nd, when Chicago Cubs manager Joe Maddon called on Mike Montgomery to walk Yadier Molina of the St. Louis Cardinals in the 9th inning.
Intentional walks are normally issued for two reasons: to bypass a good hitter for a weaker one or one who does not have the platoon advantage; and/or to set up a double play. The usefulness of intentional walks for either reason is a matter of considerable debate, and different managers have taken very different attitudes toward the intentional walk. Walter Alston even changed his approach in mid-career, moving from issuing 101 (the 8th most ever) in 1967 to just 9 (the fewest ever) in 1974.
Before Barry Bonds broke the single-season record with 68 in 2002, and then increased it to the current mark of 120 two years later, it was held by Willie McCovey, with the relatively paltry total of 45.
It should be noted that statistics concerning intentional walks have only been kept separately since 1955.
|All Time Leaders|
|Game||Andre Dawson||5||16-inning game, May 22, 1990|
|Game||Barry Bonds||4||9-inning game, May 1, 2004|
|Game||Barry Bonds||4||9-inning game, September 22, 2004|
Intentional walk with the bases loaded
|Abner Dalrymple||August 2, 1881||National League||Chicago||Buffalo||8th|
|Nap Lajoie||May 23, 1901||American League||Philadelphia||Chicago||9th|
|Del Bissonette||May 2, 1928||National League||Brooklyn||New York||9th|
|Bill Nicholson||July 23, 1944||National League||Chicago||New York||8th|
|Barry Bonds||May 28, 1998||National League||San Francisco||Arizona||9th|
|Josh Hamilton||August 17, 2008||American League||Texas||Tampa Bay||9th|
- Ted Berg: "Long live the four-pitch intentional walk!", "For the Win!", USA Today Sports, February 22, 2017. 
- Bill Deane: "Surprise Swings at Intentional Balls", in The Baseball Research Journal, SABR, Volume 40, Number 1 (Spring 2011), pp. 108-109.
- Joe Posnanski: "Anticipated rule could continue decline of IBB", mlb.com, February 22, 2017. 
- Joe Posnanski: "10 questions about new intentional walk rule", mlb.com, March 3, 2017.