For the remaining two entry periods, between February 18th to the 24th, and between February 25th to March 3rd, Amtrak will select a winner from photos posted to Instagram using hashtags #Amtrak and #WindowsPhone. You also need to follow @amtrak on Instagram.
The device being offered up to give away is not stated, but the retail price as noted on the Amtrak blog is $610.00. That probably means a Nokia Lumia 1020 or possibly a Lumia 1520 since this is a photo-centric contest. Either way, even a Lumia 925 or a Lumia 920 are not a bad freebies either.
Obviously, contests like this are for the US only. Amtrak has a number of routes throughout the country, and there are mobile apps for iOS, Android and Windows Phone. Official rules can be found at the Amtrak source link.
Sources: Amtrak via WPCentral