It's been a long time coming, but by June of next year, the 2012 Toyota Prius Plug-In Hybrid will go on sale in the U.S.

If you're eager to be one of the very first on your block to own the world's most popular hybrid vehicle--but you insist on being able to plug it into grid power--now is your moment.

This Friday, April 22, is Earth Day. Toyota has chosen that day to launch its Priority Registration system for its first modern plug-in vehicle of any kind.

Mind you, Priority Registration doesn't let you order a plug-in Prius. It just gets you into a queue that will have first access to the Online Order System when it launches later this year.

That system will let customers configure their Prius Plug-In Hybrid, choose a nearby dealership, and then track "their" cars through production, shipping, and delivery.

Toyota Prius Plug-In Hybrid prototype, tested in November 2010

Toyota Prius Plug-In Hybrid prototype, tested in November 2010

The car will launch in 15 states, including the entire West Coast (California, Oregon, and Washington), much of the Northeast (Maine, New Hampshire, Vermont, Massachusets, Rhode Island, Connecticut, New York, and New Jersey), along with Arizona, Hawaii, Maryland, and Virginia.

(Note to Hawaii residents: For reasons unspecified, you won't be able to order your Prius Plug-In online. Sorry.)

The Prius Plug-In will roll out to the rest of the United States market during 2013.

For not one, not two, but three different takes on driving the prototype 2012 Toyota Prius Plug-In Hybrid, see