Fifteen-year-old Billy Graham had made up his mind—he wouldn’t go see the traveling evangelist. The eldest of William and Morrow Graham’s four children didn’t care too much for preachers.

He was more into sports and athletes. He still treasured the memory of shaking hands with famed baseball star Babe Ruth. In fact, the teenager didn’t wash his hands for days.

“I did not want anything to do with anyone called an evangelist,” he recalled later.

Especially one like Mordecai Ham, who seemed to ignite controversy wherever he went. Ham’s style was not only to call out sin but to call out sinners in the audience and the community. He didn’t necessarily think preachers should be liked.

It sounds like a religious circus, Billy thought.

But about a month into the 11-week revival in his hometown of Charlotte, N.C., the teenager found himself in the back of the audience listening to the evangelist.

Ham opened his Bible and spoke directly and loudly from the text.

“I have no recollection of what he preached about, but I was spellbound,” Billy wrote in his autobiography Just As I Am. “In some indefinable way, he was getting through to me.”

Ham preached on subjects like money, infidelity, the Sabbath, the Second Coming of Christ, hell—and the love of God.

Bumping along in a friend’s truck on the way home to his family’s dairy farm, Billy was deep in thought. Later, he stretched out on his back in bed and stared out the window at the Carolina moon for a long time. The next night, all his father’s mules and horses could not have kept him from getting back to the meeting.

“From then on, I was a faithful attendant, night after night,” he said.

Billy was slowly coming to terms with the fact that he didn’t know Jesus Christ as his personal Lord and Savior; that he couldn’t depend on his parents’ faith or his church membership for salvation.

“Our family Bible reading, praying, psalm-singing and churchgoing—all these had left me restless and resentful,” he said. “I had even tried to think up ways of getting out of all those activities as much as I could. In a word, I was spiritually dead.”

One November night near his 16th birthday, Billy could wait no longer. When Ham gave the invitation, he got up out of his seat and joined the hundreds walking down to the front to pray for forgiveness of sins.

The world looked different the next morning when he got up to milk the cows, eat breakfast and catch the school bus.

“The Bible, which had been familiar to me almost since infancy, drew me now to find out what it said besides the verses I had memorized through the years,” he wrote.

Billy finished high school and enrolled at Bob Jones College, along with his friends Grady and T.W. Wilson, whom he had met at the Mordecai Ham meetings. Together, they started learning about evangelism.

“It was at Bob Jones College that I received my passion for the souls of men and began to realize the desperate need of a world outside of Christ,” Billy wrote. But the strict environment of the college didn’t mesh well with Billy’s free-spirited personality, so after a few months he and the Wilson brothers transferred to Florida Bible Institute. There, on the picturesque campus in Tampa, he was close to the fire of great preaching and ministry possibilities.

Students were sent out in teams wherever and whenever there was an opportunity—to churches, missions and even trailer parks. They regularly held meetings on the surrounding streets—with musical instruments, singing trios and quartets. And one or more students would preach. Watching his upperclassman stride about and shout at people at one of the meetings, Billy thought to himself: I’ll never be a preacher.

But watching Billy closely was John Minder, the 38-year-old dean of the Institute, who also had been converted at an evangelistic tent meeting at his high school.

During Easter break in 1937, Minder invited Billy on an excursion to Lake Swan, about 140 miles away, where Minder had established the Melrose Gospel Tabernacle and Bible Camp. On this trip, Minder introduced Billy to his friend Cecil Underwood, a pastor in nearby Palatka. During the conversation Cecil turned to Minder and said: “Mr. Minder, would you preach for me tonight?” Minder shot back: “No. Billy’s going to preach!”

A stunned Billy immediately declined. His repertoire consisted of four sermons, which he had only practiced, not preached. But Minder wouldn’t let Billy pass up this opportunity to get his feet wet. “You go ahead and preach,” he said. “When you run out, I’ll take over.”

When Billy stepped up to the podium that night, he rapidly delivered everything he had in less than five minutes. When he sat down, Minder went to the pulpit to tie up loose ends and call on the congregation to respond to the message.

Not long after, Billy began to feel a strong tug in his spirit, much like he had at the Mordecai Ham meetings in 1934. In the 18 months since arriving in Florida, he had begun to develop some skills he didn’t know he had.

“I knew that I loved to tell people the Good News of God’s salvation in Jesus Christ,” he wrote. “On Sundays, I often preached on the streets of Tampa, sometimes as many as five or six times a day.” He preached in the Tin Can Trailer Park, where wealthy people from northern states set up living in the summer. Crowds from 200 to 1,000 came to hear him, and many confessed faith in Christ.

Was God calling him to full-time preaching? For weeks, Billy paced the deserted streets of Temple Terrace struggling with the Holy Spirit.

“I used all kinds of rationalizations to convince God to let me do something else,” he wrote. [But] the inner urge would not subside. Finally, one night, he got down on his knees at the edge of one of the greens. He prostrated himself on the dewy turf. “Oh God,” he sobbed. “If you want me to serve you, I will.’”

The moonlight, the moss, the breeze, the golf course—all his surroundings stayed the same. There was no voice from above. But in his spirit, Billy knew he had been called to the ministry.

And he knew his answer was yes.