The southern most tip of Philadelphia is the Philadelphia Technology Park. A hotbed of technology thanks to Philadelphia's attempt to become the next big technological darling of America, this quickly attracted the attention of the Outcasts of the Brotherhood. The entire park is patrolled by Outcast robots as it's far too big for the soldiers themselves to cover. As you approach the center of the Island you'll find more power armored soldiers in the patrols. While they aren't directly dangerous to wastelanders, they are very protective of the technology they've been harvesting. It's probably best to avoid the big scary men in power armor altogether.