CHARLOTTE, North Carolina (CNN) -- Franklin Graham was stumped. He had no idea what to give his father, evangelist Billy Graham, for his 90th birthday Friday.
The Rev. Billy Graham speaks at a crusade in Kansas City, Missouri, in October 2004.
Suddenly, it dawned on him.
"I have people who sometimes come up to me and say, 'Franklin, I know I'll never meet your father, but would you mind telling him that I got saved in his meeting in London in 1950?' " the younger Graham said at the Billy Graham Library in Charlotte, North Carolina.
"I thought, wow, wouldn't it be something if everybody just wrote that little story down and gave it to him?"
So Franklin Graham turned to the Internet to help.
For the past few months, people from around the world have been leaving personal messages for the elder Graham at billygraham90.com. The Billy Graham Evangelistic Association says it has received tens of thousands of birthday greetings. Read the messages
"In 1995, I was in between combat tours," writes a Canadian veteran. "I was in my barracks room one night, and I was seriously contemplating suicide. Before cutting my wrists, a voice told me to put on the television. There you were preaching about why we shouldn't hurt ourselves that suicide wasn't the answer. I was loved that night."
Other well-wishers write about how Graham's ministry healed their marriages, reconciled families and led them to lives of service.
At 90, Billy Graham remains "America's pastor."
In over 70 years of ministry, Graham has preached to more than 215 million people in person and in 185 countries. Millions more have read his books and seen him on television. Graham has also prayed with and counseled every American president from Harry Truman to George W. Bush.
After Barack Obama won the presidential election, Graham issued an appeal on behalf of the president-elect: "I urge everyone to join me in pledging our support and prayers as he begins the difficult task ahead."
Republican presidential candidate Sen. John McCain visited Graham at his home over the summer.
"He didn't ask for one thing except for water," Franklin Graham said of the senator's visit. "He said, 'Dr. Graham, I'd appreciate your prayer. If you'd just pray that I'd run an honorable campaign,' and that's all he asked. He didn't ask for my father's support."
Today, Billy Graham spends most of his time in the remote western North Carolina mountain home where he and his wife, Ruth, raised their five children: Gigi, Anne, Ruth, Franklin and Ned.
"There are a lot of miles on that body," his daughter Ruth said. "His world has become smaller."
He leaves his home only for doctor's visits in Asheville and an occasional Billy Graham Evangelistic Association board meeting in Charlotte.
It has been a difficult time for Graham. In summer 2007, his wife, Ruth, died after being bedridden for many years. The grief is still constant for Graham.
"She was just one great woman. She has a lot of steel in her and a lot of determination. ... I just thank God that he chose her way off in China somewhere to come back to America and marry me," Graham told CNN's Kyra Phillips in one of his last television interviews in 2005.
Graham's family and associates say that his mind is sharp despite his age and that for a man who is 90, he's in good physical shape.
"The lion still has a roar," said Graham's spokesman, Larry Ross.
Graham exercises with a physical therapist on a regular basis and still swims and takes walks when he can. However, the fragilities of old age are also a reality.
In October, Graham spent a night in the hospital after tripping over his golden retriever, Sam. A nurse stays with him around the clock. Graham uses a walker to get around. His hearing is failing. Macular degeneration is stealing his eyesight.
Yet despite these obstacles, Graham continues his ministry. With the help of an assistant, Graham is writing another book about growing older.
"I have discovered that just because we grow weaker physically as we age, it doesn't mean that we must grow weaker spiritually," Graham said in a statement this week.
"In fact, we ought to be growing stronger spiritually, because our eyes ought to be on eternity and Heaven -- on the things that really matter."
In many ways, these days Graham is making up for the years he spent on the road.
"He really tried to stay in touch with us and be the kind of father that he wanted to be," his daughter Ruth said. "He has said that he's frustrated that he wasn't home for us when we were little."
His daughter Anne, a Raleigh, North Carolina-based evangelist, often stops by to read from the Bible and preach. Graham has often said she is the best preacher in the family.
Every Sunday when he is in town, Franklin has lunch with his father. They talk about the ministry and world events. Graham stays connected to the world by watching the news. CNN's "Larry King Live" is part of his nightly ritual, Ross says.
Graham often prays for the people he sees in the news. After a church shooting in December in Colorado left five people dead, Franklin says, his father was heartbroken. "He said, 'Franklin, let's pray for those families' ... so I turned the television off, and Daddy prayed for those victims, and that's the side of Billy Graham I don't think people realize."
A family meal of North Carolina barbeque, including pulled pork and coleslaw, will mark Graham's birthday Friday.
All of Graham's children and most of his grandchildren and great-grandchildren will be there. It will be the first time Graham's children have all been together since their mother died.
The following week, there will be a larger celebration with friends and people who have served with Graham. There, he will be presented with the book of birthday greetings from fans around the world.
Graham's children say that despite his remarkable life, he is a humble man who doesn't dwell on the past.
"My father doesn't look backwards," his daughter Ruth said. "He really does see that God was the one who did it, and he just happened to be in the room."
All About Billy Graham