Gilgal was close to the Jordan River and thus relatively far from Philistia (which was in the west). It would have been a safe place for the Israelites to gather without undue fear of an attack.1 It was also a historical site where the people remembered God’s past acts in their history, and it is the place which Samuel specified in his earlier instructions to Saul (see 1 Samuel 10:7–8).
4 And all Israel heard it said that Saul had defeated the garrison of the Philistines, and also that Israel had become a stench to the Philistines. And the people were called out to join Saul at Gilgal.