The sinister, unnatural "plague" got started in the Astrodome in 1966, thanks to the Monsanto Corporation, but it did not start to spread until the 1970s, when it quickly reached epidemic proportions. From 1970 until 1990, only one new major league baseball stadium had a grass field: Arlington Stadium, in Texas. Fourteen stadiums used artificial turf on at least part of the field during some or all of the years that major league baseball was played in them, but no more than ten did so at any one time. Four of these stadiums actually had real grass when they first opened. (One stadium, Comiskey Park, had an artificial turf infield from 1969 through 1976, but the outfield was always grass. It was the only dual-turf baseball stadium in the major leagues.) Candlestick Park was the first all-artificial turf stadium to go back to using God's natural green grass in 1979, and three others eventually followed suit. For the six domed stadiums, grass was simply not a "viable option," as they learned the hard way in Houston. For the seven open-air stadiums, the leading rationales for adopting artificial turf were ease of maintenance and the need for durability during those months when the field was subject to multi-sport use. Indeed, ten of these stadiums are classified as "doughnut clones" (or "cookie cutters"), but six stadiums in that grouping never had artificial turf. There have been two baseball-only stadiums with artificial turf: Royals (Kauffman) Stadium and Tropicana Field. Eight baseball stadiums had artificial turf from the beginning until the end, and two others had artificial turf for all but one or two years of their existence. Now that the Minnesota Twins have left the Metrodome, as of 2010 the only remaining stadiums with artificial turf will be Rogers Centre in Toronto, and Tropicana Field in St. Petersburg. Work is underway to convert the Rogers Centre infield to the normal dirt configuration (as Tropicana Field has had all along), with a possible convertion from artificial turf to grass in the years to come.