As you can see on Angel Island the area is very protected and no one can escape because there is barbed wire, towers, and grids.
This is a video that shows the island compounds with the barbed wires, grids and more.
Here is where the people were interrogated when they arrived on the island.
Here is a public bathroom where the people took a shower and other things.
Angel island is a beautiful island but you can see here it looks like a prison, and the detainees were the Asian peoples and after long arduous interrogations these people finally were allowed in America and became citizens.