And the angel of the Lord spake unto Philip, saying, Arise, and go toward the south unto the way that goeth down from Jerusalem unto Gaza, which is desert.
Note 1 at Ac 8:26: Gaza was an ancient city of the Philistines that was inhabited long before Abram came into the land of Canaan (Ge 10:19). It was located on the main trade route between Egypt and Mesopotamia and was frequently mentioned in Old Testament scripture (Jos 10:41, 11:22, 15:47; Jdg 1:18, 16:1, 21; 1Sa 6:17; 2Ki 18:8; Jer 47:1, and 5). The Lord prophesied the destruction of Gaza because of its wickedness (Am 1:6-7, Zep 2:4, and Zec 9:5); this came to pass in 96 B.C. under Alexander Jannaeus (The Antiquities of the Jews, Book 13, Chapter 13, Section 3).
In 62 B.C., Pompey gave the jurisdiction of Gaza to Syria, and Gabinius, the Roman governor of Syria, rebuilt the city in 57 B.C. on a site closer to the sea (approximately two and a half miles from the sea). The new site was sometimes referred to as Gaza by the Sea and the old site as Desert Gaza. It is possible the terminology used by Luke in this verse is designating the old site.