Charles S. Roberts started Avalon Hill in 1954 as a mail-order business out of his garage in Avalon, Maryland. Two years prior, Roberts had created Tactics, one of the earliest board wargames designed for mass-market production. Tactics featured several game mechanics which have since become standard for board wargames, such as variable movement costs and a combat results table. In 1958, Tactics II was released, providing a slightly revised version of the original game.

Roberts also released Gettysburg that same year. Not only was Gettysburg the first board game to be based on an actual historical battle, but the second edition of the game, released in 1961, introduced the hex map. Hex maps, or hex grids, have since become commonly used in all types of games, ranging from wargames to board games to role-playing games and even many different types of video games.

The advantage of the hex grid over a traditional square grid map is that the distance between the center of each individual cell is exactly the same in a hex grid. On a square grid, moving diagonally is a greater distance to traverse. Hex grid cells also always share an edge with their neighbors and never connect to another cell at only a point.

Avalon Hill moved out of a garage and into a proper office building in Baltimore in 1959, and the company started publishing games from other designers as well, such as Verdict, and the various sports-themed Baseball Strategy, Football Strategy, and Basketball Strategy.

In the early 1960s, the economy hit a recession, and Avalon Hill was faced with a large amount of debt. Roberts had planned on filing bankruptcy at the end of 1963, but instead, Monarch Office Services and J.E. Smith & Co., his creditors, took over the company. The company retained just one original staff member, Thomas N. Shaw (responsible for designing the sports Strategy games), appointed J.E. Sparling as the president, and adopted a twice-per-year game release schedule.

Though Roberts left the gaming industry at this time and never really returned to it, the Charles S. Roberts Award was created in his name at the first Origins Game Convention in 1975, and has been given out in recognition of excellence in historical wargaming. Roberts himself went on to form a small book publishing company – Barnard, Roberts and Company, Inc. – where he wrote several books about railroad history. He passed away in 2010.