Five game-changers baseball.

It's often been said that baseball has changed so little through the generations that it's essentially the same game that your grandfather used to play and watch.

But there have been subtle and even dramatic changes in the culture and environment in which the game has been played over the last 75 years, not to mention changes in rules and equipment. There have also been signature events that have impacted or revolutionized the game.

Here are five of the most significant game-changing moments:

1 INTEGRATION

In the most significant cultural change in the game's history--not to mention one of the most significant in American history--Jackie Robinson broke the color barrier in 1947 by becoming the first African American to play in the major leagues. Robinson, playing first base for the Brooklyn Dodgers after a distinguished football and track career at UCLA, went on to win National League rookie of the year honors. Four more African Americans made their big league debuts that year.

Within a decade, the old Negro Leagues had dried up as African-American players began making their mark in the established major leagues as a matter of course. Soon players like Hank Aaron, Bob Gibson, and Willie Mays became the elite players in the game.

Nowadays, baseball has not only become a fully-integrated sport domestically, but the game has become global in scope with about 27 percent of all major league players coming from countries beyond the boundaries of the United States, principally the Dominican Republic. Where Puerto Rico's Roberto Clemente once was one of the few foreign-born players on the major league landscape, players like Japan's Ichiro Suzuki, the Dominican's Vladimir Guerrero and Venezuela's Miguel Cabrera are among the game's international stars.

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2 THE DESIGNATED HITTER

The most significant rule change in the game came in 1974 when the designated hitter was introduced to the American League on an experimental basis, with the Yankees' Ron Bloomberg becoming the game's first DH. The National League refused to go along initially and maintained that stance even as the rule gained widespread acceptance at levels from the majors to the minors to the colleges to the high school and youth league levels--and even internationally.

The motivation for the DH rule was to inject more offense into the game after it had fallen to dangerously low levels in the late 60s and early 70s. Pitchers were simply dominating the game to a degree not seen since the Dead Ball Era at the turn of the century.

In direct response to a 1968 season in which Boston's Carl Yastrzemski won the American League batting title with a .301 and St. Louis' Bob Gibson led the National League with a record-low 1.12 ERA, the height of the pitchers' mound was lowered from 15 to 10 inches. When offense continued to sputter, the AL, at the urging of commissioner Bowie Kuhn, stepped forth with a revolutionary concept that substituted a legitimate hitter into the batting order in place of the traditionally weak-hitting pitcher.

3 ALUMINUM BATS

The most significant equipment change in the game's modern history was the implementation of aluminum bats in 1973 at the college, high school and youth league levels. The change from wood to aluminum at the grassroots levels was made ostensibly as a cost-saving measure. More durable aluminum bats simply lasted much longer than increasingly expensive wooden bats.

But as aluminum bats became lighter and increasingly more streamlined, they provided a greater sweet spot and resulted in such an upsurge in offense that baseball was more like pinball than the game that was played with wood. By 1996, NCAA Division I-wide records were set for batting averages, home runs and earned run averages, prompting stricter standards in the construction of aluminum bats. Predictably, the level of offense tapered off over the next decade.

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4 THE CLOSER

From a strategic standpoint, the most significant change in the way the game has been played over the last 75 years has been the use of relief pitchers, specifically closers.

Where at one time the complete game was a matter of routine for starting pitchers and relievers were viewed as simply not being good enough to start, the game evolved in the 1970s and 1980s to a point where pitchers like Rollie Fingers, Goose Gossage and Bruce Sutter were being successfully employed as late-inning specialists.

They often pitched two or three innings while closing out games.

Soon the job of a closer became so specialized that he would customarily work only the ninth inning while other relievers, or setup men, would work the seventh and eighth innings. With starting pitchers working fewer and fewer innings as four-man rotations morphed into five-man rotations and pitch counts became a baseball buzzword, the role of setup men became increasingly important as they effectively served as the bridge between the starter and closer.

The save, the statistic that measures a closer's contribution to his team's victory, was recognized as an official statistic in 1969. The criteria for earning a save was modified a couple of times in the next few years but was established in its present form in 1975.

But the save was not the only statistic that helped to revolutionize the modern game.

Statistical analysis to measure player performance has become so sophisticated over the last quarter century that traditional tools like batting average and earned run average have been augmented and in some cases even replaced by more encompassing measurements like on-base percentage, which became an official statistic in 1984, and the more revolutionary OPS--a term that combines a player's on-base percentage and slugging percentage.

5 THE 1975 WORLD SERIES

Just as Babe Ruth's home run exploits reinvigorated the game in the wake of the Black Sox scandal some 50 years earlier, night baseball signaled a new era for the game in the 1930s and the end of World War II ushered in a new period of prosperity, a dramatic 1975 World Series gave the game a kick start at a time when it most needed it. Interest in baseball had begun to wane in the 1960s and early '70s--partly for self-induced reasons, partly because society was changing.

The onset of television and air conditioning began a slow decay in the game's popularity in the '50s, particularly at the minor league level. The dominance of one team, the New York Yankees, further eroded baseball's fan base in areas outside New York. And young people were no longer relating to baseball's passive pace, particularly as the unpopular Vietnam War raged. The confluence of TV and the violence of the Vietnam War played rights into the hands of football, which soon became America's passion--baseball merely America's pastime.

But the 1975 Series, a tension-packed, back-and-forth series between the Boston Red Sox and Cincinnati's Big Red Machine, opened America's eyes to baseball again. And over the next 30 years it led to a wave of prosperity the game had never known, ranging from widespread stadium construction to record attendances--no matter the accompanying labor strife and record player salaries.

In 2005, the game set all-time attendance records at the major and minor league levels, a sign the game is every bit as popular now as it ever was 75 years ago.

By Allan Simpson, Founding Editor, Baseball America