If you look through the countless connected words, you'll find the story behind the 60-year marriage of a Boulder couple.

The husband and wife, both in their 80s, sat down with 9NEWS and shared something they've saved from before their marriage that shows the foundation of their love.

The couple credits many things that have kept their relationship tied together: Bob and Judy Rothe like to play cards with friends, they go to church together and they share a love for children. They've got four of their own and have cared for many others including more than 90 foster children.

“We're hosting our 115th Out With People Student right now,” Bob said.

They've shared many memories together in their home in Boulder, but their relationship started in college.

“Every night we would sit out in the car parked, 'discussing philosophy,'" Bob said.

They got engaged, but for over a year, their relationship would be long distance.

So, they wrote over 700 letters while they were apart and told each other how much they loved and missed them. They planned to open the letters on their 25th wedding anniversary, but that didn't happen.

“We finally decided - if we are going to do it while we're still alive, we better do it,” Bob said.

Back to why their relationship has lasted so long: they said respect and commitment play a large part, but they added you can't count out humor.

“We knew we wanted to start a family which we did almost immediately, but we don't know where the first two came from," Bob said, laughing. "You always joke about that.”

For them, the letters are more than ink on paper.

“It's something that you can hold and feel their closeness,” Bob said.

They've kept that closeness for more than six decades and, thanks to what's in the box that holds the letters, they can remember the love they shared and still do.

Those letters continue to get attention. The couple heard from a woman who plans to take the letters and turn them into a musical.