The mail machines are working overtime at the Billy Graham headquarters in southwest Charlotte as the famous Charlotte-born evangelist approaches 90. Tens of thousands of birthday cards and letters have poured in, filled with memories and good wishes.

Ken Barun with the Billy Graham Evangelistic Association showed Eyewitness News the hundreds of cards that piled up over one day – the same amount that’s been coming in for weeks.

“Happy 90th birthday, you still have unfinished work here on Earth,” one card reads.

“We heard you in person at the Seattle Kingdom in the 1980s,” another reads.

Some have pictures, while all have warm thoughts, like “What a blessing you have been."

There are e-mails too. A pastor wrote, "My sister and brother-in-law attended one of your films and got saved. God bless you abundantly."

Gastonia mother Becky Beavers wrote, "I want you to know you have made a great impact on our lives. Please remember my son, Austin, as you pray."

Beavers shared her e-mail with Eyewitness News and introduced a news crew to 13-year-old Austin. The teen may represent the next generation of Graham followers. He has a full video collection and knows most of the sermons by heart.

Beavers said Austin has been watching the old crusades for years.

"His message is simple. A child can understand it. And it just touched something in him," she said.

Many of the birthday greetings are being assembled into a book for Graham. One such greeting is from a woman in Florida. She sent in a photo from 1938 with Graham circled in red.

There's also a card from President George W. Bush and his wife, Laura.

A heartfelt letter also came from former first lady Nancy Reagan. She wrote, "When I lost Ronnie, you reassured me of what I most needed to hear -- that we will be together again someday. That promise has kept me going ever since."

Barun said Graham has similar thoughts about his own wife, Ruth, who died last year. But he's still very excited about turning 90.

“He's certainly not thinking about dying being an end of things, of course. To him it's just going to another place. And he's said I know where I've been, I know where I am, and I certainly know where I'm going,” Barun said.

Graham’s 90th birthday is Friday.

You can go to the Billy Graham Library to wish Graham a happy birthday by video. The library is hosting a two-day celebration where guests can tape a 30-second birthday message. There will also be birthday cake and a special keepsake for each guest.

The celebration is free to the public. It will be from 9:30 a.m. to 5 p.m. Friday and Saturday. Franklin Graham will make a special appearance at 11:45 a.m. Friday.

You can also send Graham a birthday message by e-mail. Look for the link in the sidebar.