Love is in the air, and the post, in the US city of Loveland.

Every year, tens of thousands of people from around the world route their Valentine’s Day cards to the “Sweetheart City” in Colorado to get a special inscription and the coveted Loveland postmark.

The re-posting tradition has been going on for nearly 80 years and is the largest of its kind in the world, according to Mindy McCloughan, president and chief executive of the Loveland Chamber of Commerce.

At its height, volunteers processed more than 300,000 items of post per year. That number dropped to 100,000 to 125,000 as people turned to email and social media messaging.

Volunteers dressed in Valentine-themed garb gather before the big day to stamp thousands of envelopes with the special postmark.

“Love is our message – Hearts are our brand. Happy Valentine’s Day from the City of LOVEland,” the postmark reads in part.

One of the more seasoned volunteers, Joyce Boston, 89, has been stamping since 1997.

“What do I get out of it? Is a lot of new friends. Friendship. Spreading love. I love spreading love,” she said. ”And I love doing volunteer work. It keeps me, gives me a reason to keep living. Yes. Keeps me young.”

Loveland also holds a Sweetheart Festival, crowns a Miss Loveland Valentine and is decorated year-round with hearts, attached to lampposts and featured in murals.

The city has a large metal Love sign at the visitors’ centre, where people attach padlocks engraved with names and messages of love.

McCloughan said: “In a time when there is such uncertainty in the world, what greater thing to do than to share love and compassion and hope with those around the world when it’s just time when it’s needed most?”

The programme receives mail from all 50 US states and 110 countries.