In A.D. 324, Constantine became the undisputed ruler of the whole Roman Empire. Once secured in that position, Constantine demanded that persecution of Christians stop. Between the death of Christ around A.D. 33 and the rise of Constantine's father, Constantius Chlorus, to caesar of the Western Roman Empire in A.D. 293, Christians were persecuted throughout the empire. Constantine's father, needing a base of support, stopped Christian persecution in the West. But in the East, Christians were still routinely persecuted.
Persecution was not a great recruitment strategy: "Accept Christ, be food for the lions!" The early church had to do something to persuade people that Christ was real, Christianity was the true religion and persecution in this existence was nothing compared to eternal life with Christ.
Thematically, the early church knew 40-day periods had significance. Christ spent 40 days in the desert. Noah spent 40 days of rainfall on the ark. Elijah spent 40 days traveling to Mount Horeb. The early church decided it would train and educate potential converts for the 40-day period leading up to Easter. On Easter, those who understood what they were getting into would be baptized and welcomed as brothers and sisters into the church.
This all started before wide circulation of the letters that would become the New Testament. In some cases, churches had copies of Paul's letters before the gospel letters. Mark wrote Peter's account possibly around A.D. 40, though some put it after A.D. 70. There is consensus that John wrote his gospel letter around A.D. 90, well after Paul's letters had begun circulating. But no one had yet put them all together.
The earliest creeds, including the Old Roman Creed, which evolved into the Apostles' Creed, became chief instruments of teaching when the apostolic letters were unavailable. Each line became a point of study over the 40 days. "I believe in God, the Father Almighty" would be studied for a week. "And in Christ Jesus His only Son, our Lord" would be the next week and so on. The Old Roman Creed -- which left out the descent into hell but otherwise was the basic Apostles' Creed -- became a foundation of faith. By about A.D. 200, the creed was fully in the form we have today.
New Christians would study what the creed meant and rely on the oral histories spread through the church. Within about 100 years of Christ's death, the apostolic letters that would form the New Testament entered wide distribution through the Empire.
After A.D. 324, the great troubles went away, and anyone could become a Christian. In fact, many claimed to be converted just to have access to the emperor. Some, without the tests and turmoil of persecution, wanted to show their true commitment to the faith. They abandoned their urban existence, sold their possessions and lived as hermits in the wilderness -- like Christ did for those 40 days. They were called "monachos," or monks.
The church itself kept that 40-day period and called it the "Quadragesima," meaning 40th. As the traditions of Christianity spread north into Germanic-speaking territories, the Quadragesima became associated with springtime, the season of study and baptism. The Germans called this season Lenz, and it evolved into Old English and Dutch as the Lenten season, or Lent.
Though many American protestant denominations do not actively practice Lent in the way Catholics do, it is worth remembering where it comes from. The early church, before Bibles and book publishing, needed converts to know their faith and honestly commit to it. Converts needed to understand why they might be persecuted. Given the shallowness of most American Christianity these days, perhaps it is worth considering.
Christianity in America has become increasingly superficial. Liberal Christians want to steer orthodoxy toward popular culture. Every denomination that has done so has begun to rapidly decline. Others have turned Sundays into feel-good pep talks. The increased superficiality of Christianity corresponds to its decline. Perhaps churches need to go in the other direction and actually do as the early church did -- train up new believers in what Christianity really means.