According to history, the Island was once a part of the continent of Downunda, and home to the Echidna city of Echidnaopolis. However, a massive body known as the White Comet came towards the area on a collision course. (This differentiates it from the Black Comet, but the Black Comet is much smaller, and its velocity is much lower; it wouldn't have been a threat, as it can't pierce a planet's atmosphere under its own power.) In order to save themselves, the Echidnas used twelve Chaos Emeralds to raise their city and a portion of the surrounding area into the sky, thus creating the Floating Island and the Great Crater. The Island was renamed Angel Island after the Echidna Angel-La, mother of Edmund the first guardian.
Angel Island serves as the battleground between the Brotherhood of Guardians and its allies against the Dark Legion. The battle has raged for centuries, beginning after Dark Legion leader Dimitri absorbed the energies of eleven of the Island's original emeralds and became the first Enerjak. After Enerjak's defeat, Dimitri's son Menniker founded the Dark Legion in opposition to technology bans, resulting in the Legion becoming a sort of technocratic cult. The battles have had many catastrophic effects, and the island was rendered uninhabitable for a time in response to a nuclear attack by the Dark Legion. In order to protect the citizens, the Guardian of that period transported the city of Echidnaopolis into another zone.
The Island is also home to the Dingoes, a race who by and large despise their Echidna neighbors. This has led to them being minor antagonists in the series. (This is a nod to the relationship between real-world dingoes and echidnas, in which dingoes are efficient echidna hunters.) Eventually, this led to the Dingoes siding with Dr. Robotnik, taking over Angel Island before being defeated by the joint efforts of the Chaotix and the Dark Legion. The Dingoes continued to menace the island, but eventually found themselves facing a new adversary in the form of the Destructix. Because of their efforts, the group of escaped criminals earned their leader, Dr. Finitevus, the position as Angel Island's caretaker from Locke. After Finitevus managed to resurrect Enerjak, the Island began moving towards New Mobotropolis, obviously directed by Enerjak in his quest to conquer all of Mobius.
A Map of Angel Island
Major Locations:
1) Shrine Isle
2) Launch Base
3) Strawberry Fields
4) Mushroom Hills
5) Hydro City
6) Swampy Swamp
7) Hapyland Amusement Park
8) Royal Compound
9) Sandopolis Desert
10) Eternal River
11) Tasmanian Ruins
12) Azure Lake Oasis
13) Forbidden Zone
14) Haven
15) Grand Conservatory
16) Fire-Ant Hill
17) Rainbow Valley
18) Knuckles' Burrow
19) Echidnaopolis Ruins
20) Cavem Canus
21) Destroyed Dark Legion Base
22) Lake Nessie
23) Mount Fate
24) Marble Garden
25) Rocky Hill
26) Lava Reef
27) Red Mountain
28) Mount Osohai
29) Hidden Palace
30) Mount Thunder
31) Sky Sanctuary
32) Ice Cap
Residents of Angel Island:
Knuckles the Echidna
Julie-Su
Archimedes
Groups:
The Chaotix
The Brotherhood of Guardians
The Dark Legion
The Dingo Army
