Monday is the 50th anniversary of a baseball milestone.
On April 18, 1966, the Astros hosted the Dodgers in their home opener at the Astrodome in Houston, in the first Major League game played on artificial turf, which at that point covered only the infield. The occasion began in style, with Los Angeles speedster Maury Wills hitting a single to center field in a contest that featured two future Hall of Fame starting pitchers, the Dodgers' Don Sutton and the Astros' Robin Roberts.
L.A. eventually triumphed, 6-3, and in the half-century since, MLB has traveled nearly full circle when it comes to artificial turf. First, it was all the rage, springing up in ballparks across the league. Then the pendulum swung the other way, to the point where AstroTurf (and its relatives) have almost vanished from the highest level of baseball.
Only two current ballparks do not feature natural grass: Tampa Bay's Tropicana Field and Toronto's Rogers Centre. However, with the latter debuting a new dirt infield this season, the turf infield, at least, is now extinct.
With that in mind, here are some facts to know about the history of artificial turf in baseball as we honor this anniversary.
• The Astrodome opened with a natural field in 1965, but when the roof had to be painted so outfielders could see fly balls, the grass proved unable to survive and the team turned to an artificial surface the next year. The Monsanto company provided what was originally known as "ChemGrass," before it wisely was redubbed AstroTurf. It was installed in the infield only at first but was expanded to the outfield later in the season, with the first game on a complete AstroTurf field taking place on July 19, 1966, in an 8-2 win over the Phillies.
• It wasn't long before the Astrodome had company. Chicago's Comiskey Park (then called White Sox Park) became the first American League stadium and the first outdoor stadium to take the plunge -- but only part-way -- in 1969. Turf replaced grass in the infield and infield foul territory, but not in the outfield and its foul territory. That experiment ended after the '75 season, with the Sox returning to a 100-percent natural grass.
• By 1973, artificial-turf fields had opened in Cincinnati, Pittsburgh, Philadelphia and Kansas City, while St. Louis and San Francisco converted from grass to turf. By '82, the White Sox and Giants had returned to grass, but there was turf in Montreal, Toronto, Seattle and Minnesota. Toronto's SkyDome (now Rogers Centre) entered the fold in '89, replacing Exhibition Stadium and capping the movement.

• Cincinnati's Riverfront Stadium was the first park, in 1970, to have artificial turf cover the entire infield, with the exception of the pitcher's mound, the home-plate area and "sliding pits" around each base. But several other parks adopted or opened with this style, which survived until Rogers Centre's new infield was put in for this season.
• An entire postseason series was played entirely on artificial surface as early as 1970, when the Reds and Pirates met in the National League Championship Series. Cincy won the first postseason contest on turf, at the Pirates' Three Rivers Stadium, and went on to a three-game sweep. The Reds then hosted the first such World Series game, losing to Jim Palmer, Brooks Robinson and the Orioles in the opener, as Baltimore went on to take the Fall Classic in five games.

• The era of the multipurpose, artificial-turf stadium changed the game noticeably, with teams such as Whitey Herzog's Cardinals of the 1980s taking advantage of the turf with speed, defense and a small-ball approach. But there were other side effects. That included some unpleasant conditions when summer heat met AstroTurf. For example, on one day in 1970, The Associated Press reported that a thermometer placed in Busch Stadium's artificial surface revealed a ground-level temperature of 152 degrees.
• Since 1990, the only turf field to open has been Tropicana Field, home to the then-Devil Rays expansion team in 1998. However, the stadium actually was finished eight years earlier in an effort to attract an MLB team. The Trop initially used AstroTurf but in 2000 switched to FieldTurf, becoming the first major professional facility to do so.
• From the peak of 10 teams (out of 26) playing on turf, the number began to dwindle. From 1995, when Kauffman Stadium in Kansas City converted to natural grass, to 2010, when Target Field replaced the Metrodome in Minneapolis, nine of the 10 turf fields fell by the wayside thanks to replacement grass, a new ballpark or a move (Montreal to Washington).
• Many memorable baseball moments have occurred on turf over the years. A very small sampling of those: Pete Rose runs over Ray Fosse at home plate in the 1970 All-Star Game in Cincinnati; Roberto Clemente picks up his 3,000th hit -- his last before his tragic death -- in Pittsburgh on Sept. 30, 1972; Hank Aaron hits his 714th home run to tie Babe Ruth on April 4, 1974, in Cincinnati; Rose breaks Ty Cobb's all-time hits record with No. 4,192 on Sept. 11, 1985, in Cincinnati; The Reds' Tom Browning throws a perfect game, the fifth in NL history, against the Dodgers in Cincinnati on Sept. 16, 1988; Jack Morris tosses a 10-inning shutout to outduel John Smoltz as the Twins beat the Braves, 1-0, in Game 7 of the 1991 World Series at the Metrodome; Phillies second baseman Mickey Morandini turns baseball's first unassisted triple play in more than two decades against the Pirates in Pittsburgh on Sept. 20, 1992; Joe Carter wins the World Series for the Blue Jays with a walk-off homer in the bottom of the ninth inning of Game 6 of the 1993 World Series; The Padres' Tony Gwynn gets career hit No. 3,000 Aug. 6, 1999, in Montreal; Carlos Delgado becomes only the fifth American League player to homer four times in a game on Sept. 25, 2003, against Tampa Bay at Toronto.

• While not in the same category as the moments mentioned above, one of the strangest games in baseball history also unfolded on turf. On July 2, 1993, Veterans Stadium hosted a doubleheader between the Phillies and Padres. The first game started at 4:35 p.m., but thanks to bad weather, the nightcap did not get underway until 1:28 a.m. and finally wrapped at 4:41 a.m., setting an all-time record for the latest finish, according to Elias. The winning play was fittingly bizarre, as Phillies closer Mitch Williams -- who later that year served up Carter's homer -- smacked a walk-off single against Trevor Hoffman in the 10th inning for one of his three career hits.
"I've never been through anything like this," Williams said afterward. "I stayed because I had to."