Love is in the air ... and the mail ... in the northern Colorado city of Loveland. Every year, tens of thousands of people from around the world route their Valentines to the “Sweetheart City” to get a special inscription and the coveted Loveland postmark. The re-mailing tradition started nearly 80 years ago and is the largest of its kind in the world. At its height, volunteers processed more than 300,000 pieces of mail per year. That number dropped to 100,000 to 125,000 as people turned to email and social media messages. The program receives mail from all 50 states and 110 countries.