RPM is the acronym used for revolutions per minute. It measures the number of revolutions completed in one minute around a fixed axis, giving the speed of a mechanical component. It is commonly used to describe the performance of automobile engines.
Like most ballparks built from the 1990s onward, Safeco Field is a 'retro-modern' style ballpark that incorporates many of the features of ballparks built in the 1950s and earlier with modern amenities.
Here's a timeline of how Wrigley Field (Weeghman Park when it was first built) was constructed, and the various changes that have been made to it over the years. 1914: Opened April 23 as the home of the Federal League Chicago Whales, with a single deck that seated 14,000.