Philippi was a capital city of ancient Macedonia. King Philip of Macedonia, the father of Alexander the Great (see Alexander The Great In Prophecy), named the city after himself. By the time of the decline of the Greek Empire (see Ancient Empires - Greece) and the rise of the Roman Empire (see Ancient Empires - Rome), Caesar Augustus (the same Roman emperor who called the famous census that caused Jesus Christ to be born in Bethlehem) made it a Roman military colony (colony: "a body of people who settle far from home but maintain ties with their homeland") with the purpose of ruling the surrounding district for Rome. The Messiah (although He had ascended to heaven, He was managing His servants of the Gospel) had the apostle Paul (see Paul's Ministry) go there, thereby taking the Gospel from Asia to Europe.
"from thence to Philippi, which is the chief city of that part of Macedonia, and a colony"
Paul's First Missionary Journey was in Asia Minor (i.e. Turkey) and it seems that Paul intended to remain in his "home" area (Paul was born in Tarsus, in that area of southern Turkey), but the Holy Spirit directed Paul toward Europe, across The Aegean Sea into Macedonia.
"Now when they had gone throughout Phrygia and the region of Galatia, and were forbidden of the Holy Ghost to preach the word in Asia, After they were come to Mysia, they assayed to go into Bithynia: but the Spirit ["the Spirit of Jesus" in the RSV] suffered them not.
And they passing by Mysia came down to Troas. And a vision appeared to Paul in the night; There stood a man of Macedonia, and prayed him, saying, Come over into Macedonia, and help us. And after he had seen the vision, immediately we endeavoured to go into Macedonia, assuredly gathering that the Lord had called us for to preach the gospel unto them." (Acts 16:6-10 KJV)
Paul obeyed and made the crossing that brought him to Philippi and the purpose of Paul's Second Missionary Journey.
"Therefore loosing from Troas, we came with a straight course to Samothracia, and the next day to Neapolis; And from thence to Philippi, which is the chief city of that part of Macedonia, and a colony: and we were in that city abiding certain days.
"And on the Sabbath we went out of the city by a river side, where prayer was wont to be made; and we sat down, and spake unto the women which resorted thither. And a certain woman named Lydia, a seller of purple, of the city of Thyatira, which worshipped God, heard us: whose heart the Lord opened, that she attended unto the things which were spoken of Paul. And when she was baptized, and her household, she besought us, saying, If ye have judged me to be faithful to the Lord, come into my house, and abide there. And she constrained us." (Acts 16:11-15 KJV)
Philippi was also a sailing port along Paul's Third Missionary Journey.
"And after the uproar was ceased, Paul called unto him the disciples, and embraced them, and departed for to go into Macedonia. And when he had gone over those parts, and had given them much exhortation, he came into Greece, And there abode three months. And when the Jews laid wait for him, as he was about to sail into Syria, he purposed to return through Macedonia. And there accompanied him into Asia Sopater of Berea; and of the Thessalonians, Aristarchus and Secundus; and Gaius of Derbe, and Timotheos; and of Asia, Tychicus and Trophimus. These going before tarried for us at Troas.
And we sailed away from Philippi after the Days of Unleavened Bread [see Christ's Feast of Unleavened Bread], and came unto them to Troas in five days; where we abode seven days." (Acts 20:1-6 KJV)
Fact Finder: Who wrote Philippians, the Epistle to the Christians at Philippi?