Which came first: Violent games, or non-violent games?

Was the first video-game in history a violent game, or a non-violent game? Trying to determine which category deserves the blue-ribbon for coming in first in the historic timeline was somewhat challenging, since different sources make different claims about which game actually came first. However, the weight of evidence suggests that the honors go to the "non-violent" category— even after accounting for the spirited disagreements about which specific criteria should be used to qualify or disqualify historic contenders for the title of "first video game."

The 1970's game "Pong" has sometimes been cited as the first video game (as has "Pac-Man"), but while Pong may have been a landmark game and one of the first games to become popular in arcades and home consoles, it appears to have been introduced at least a few decades after the very earliest video games.

Spacewar, a 1962 computer game featuring dueling space ships (and reportedly very popular among MIT students) appears to have been the only contender that could have given the "violent game" category the first place medal, but was preceded by a number of non-violent contenders.
Public domain screenshot of Spacewar! being played on a PDP-1 emulator. (Image from Wikimedia Commons.)
Several of these contenders in the somewhat broader "electronic games" category appeared as early as the 1940's: For example, a machine called the Nimatron reportedly appeared at the New York World's Fair circa 1940. According to Wikipedia: "Nim is a mathematical game of strategy in which two players take turns removing objects from distinct heaps," which would presumably have given the non-violent category the 1st-place prize if the Nimatron had qualified.

However, the Nimatron arguably did not qualify as a "video game," since the machine reportedly did not generate its own graphic display. The 1940's also saw the introduction of the "Cathode-Ray Tube Amusement Device," which was also an interactive electronic game, but which some disqualify for first-place honors for similar reasons.

Two more noteworthy contenders from the early 1950's include "Bertie the Brain," a 13+ foot tall computer capable of playing Tic-Tac-Toe (also known as "Noughts and Crosses"), and the 1951 Nimrod computer, which was also capable of playing Nim— but these were both disqualified for the "first video game" prize by the web site "How-to Geek," since they also used electronic displays involving light-bulbs hidden behind impressive looking screen displays, rather than generating their own internal graphics.

The web site "How-to Geek" claims that the honors for first video game go to Tennis for Two, a computer game developed by the American physicist William Higinbotham in 1958: The game was a simple tennis simulation in which players used a large aluminum controller to bat an on-screen ball back and forth over a net, all rendered in a 2d graphics display.
William Higinbotham's 1958 "Tennis For Two." (Public domain photo by the Brookhaven National Laboratory.)
Higinbotham designed the game for an exhibition at the Brookhaven National Laboratory, while he was employed as the head of the Instrumentation Division. He later recounted: "The instruction book that came with the computer described how to plot trajectories and bouncing shapes, for research. I thought, 'Hell, this would make a good game.'"

"Tennis for Two" reportedly attracted hundreds of players (particularly teenagers and young men and women), who lined up at Brookhaven National Laboratory's annual public exhibition for a turn to play the game. The game was so popular that Higinbotham also developed a 1959 edition in which players could select alternate gravity levels to simulate tennis-playing conditions on Jupiter and the Moon.

Accordingly, it appears that the "non-violent" game category is the clear winner of the "first video game in history" 1st prize, with 1958's "Tennis for Two" having preceded 1962's "Spacewar" by approximately four years.
A tennis-playing 1950's couple (Image from Cinderella Love #29. Image from, licensed CC BY 3.0)
Adding further interest to this story is the fact that the William Higinbotham, (who has been dubbed a "Grandfather" or "Founding Father" of video games) had previously worked as a physicist at the Los Alamos National Laboratory, where he headed the team of scientists that designed the electronic ignition mechanisms and measuring instruments for the world's very first nuclear bomb.
William Higinbotham's Wartime Staff Badge Photo. (Public domain photo from the Los Alamos National Laboratory.)
Higinbotham later became a co-founder and first chairman of the Federation of American scientists (a continuation of the Federation of Atomic Scientists, originally founded by Manhattan Project scientists). The FAS is still active today, and describes itself as a network of experts and thinkers motivated to "reduce nuclear dangers and ultimately prevent global catastrophe."

Higinbotham said in 1983 that he never bothered to patent "Tennis for Two," both because it "seemed to me sort of an obvious thing," and because it would have belonged to the government even if he had tried to patent it. After Higinbotham passed away, his son reportedly also stated that it was "imperative" that his father be remembered for his lifelong dedication to nonproliferation work intended to prevent nuclear disaster, and not merely his contribution to video game history.

Nonetheless, Higinbotham's contribution to video-game history has been acknowledged by many sources over the years, notably with the 2011 creation of an educational foundation named "The William A. Higinbotham Game Studies Collection." The foundation's web site states that it is "dedicated to collecting and preserving the texts and ephemera that document the history of video games; and the work of early game innovator and Brookhaven National Laboratory scientist William A. Higinbotham, who in 1958 invented the first interactive analog computer game, Tennis for Two."