Earth

Earth, also referred to as "The Ground", is the original home of humanity. The planet had been affected by radiation for 97 years after a devastating nuclear apocalypse. After the Ark's life support systems were found to be failing critically, the 100 were sent to the surface in a last ditch attempt to determine if Earth is habitable again. The 100 lived on the planet along with the Grounders, as well as the rest of the Sky People from the Ark.

Recently, Earth has been destroyed by the Second Nuclear Apocalypse, known as "Praimfaya". What used to be a lush green planet has now become a charred place left in ruins. Fortunately, Praimfaya only destroyed 96% of the Earth's surface, and an area of the planet did manage to survive the apocalypse. This area is known as the Shallow Valley.

Environment
Over the course of a century, Earth has become a very different place in the wake of the Nuclear Apocalypse that left much of the world devastated and drove mankind to near extinction. Ecosystems have changed, landscapes have been reshaped, and life has adapted.

As of now, the infrastructure that had existed throughout the land had been mostly destroyed. Any evidence of human civilization as we know it is almost non existent. Although survivable, the worlds natural flora and fauna are almost extinct.

Major Locations

 * The Ark
 * Delinquents' Camp
 * Mount Weather
 * Arkadia (formerly Camp Jaha)
 * Polis
 * Tondc
 * Dead Zone
 * Second Dawn Bunker

Art Supply Store
Also known as Finn's Bunker, it is the name given to a bomb shelter discovered by Finn Collins. The bunker's original purpose was to serve as a shelter from nuclear bombs in the case of an apocalypse, but the owners never made it. The Delinquents used it for supplies as well as a place to take shelter.

Because of the instability of the Delinquents' society, Finn convinced Clarke Griffin to keep the bunker a secret in order to have a place to hide if the needs arose. In Murphy's Law, when John Murphy was out to get Charlotte, Finn and Clarke hide Charlotte down in the bunker. After Clarke and Finn fall asleep, they wake up to find that Charlotte ran away. Later, Clarke and Finn sleep together in the bunker. After Raven Reyes arrives on Earth, Clarke takes Raven to the bunker in His Sister's Keeper to look for a transmitter to fix the radio. Raven found a remote-controlled car and used it for parts.

After capturing Delano in Reapercussions, Finn takes Bellamy Blake, Murphy, Zoe Monroe, and Sterling to the bunker to question Delano, ending in Finn executing him. Finn returns with Clarke to the bunker one last time in Fog of War when they flee from Acid Fog, coming face-to-face with Delano's corpse.

Lincoln's Cave
In His Sister's Keeper, Lincoln brings Octavia Blake back to his cave to treat her injuries. After Lincoln is captured and tortured by the Delinquents, Octavia helps him escape and he returns to his cave. Octavia meets up with Lincoln again in his cave in Unity Day and together with Finn Collins, they arrange the bridge meeting between Clarke and Anya. In I Am Become Death, Octavia finds Lincoln in his cave, packing up his belongings. He asks her to leave with him but she ultimately refuses and decides to stay behind with the Delinquents. Lincoln returns to the cave in We Are Grounders (Part 2) after outrunning Reapers and runs into Finn who convinces him to use the Reapers as a distraction to help the Delinquents during the final battle.

Oil Rig


Located away from the mainland, the Floukru‎‎ live on the oil rig.

Seen in Join or Die, Red Sky at Morning

Other Minor Locations

 * Becca's Island
 * Mount Weather Mines
 * Philpott Dam
 * Lincoln Memorial
 * Eden's Pass

Residents
According to Becca, about 6.5 billion people were killed in the aftermath of the Nuclear Apocalypse. However, some survivors remained, these included the ancestors to the Grounders, the Mountain Men, and the Sky People. The Mountain Men took refuge in Mount Weather and the Sky People survived in space for 97 years isolated from their former natural environment.

Current

 * Wonkru
 * Sky People
 * Grounders
 * Spacekru
 * Two Nightbloods  (Clarke and Madi) 
 * Eligius Prisoners

Former

 * The Grounders (left to go live on the Ark)
 * Mountain Men (deceased)
 * Reapers (deceased)
 * A.L.I.E. (terminated)
 * Floukru (deceased)

Trivia

 * Earth was still irradiated, but the Sky People are immune due to growing up around solar radiation. However, the radiation on Earth, is now gone, after the Second Nuclear Apocalypse.
 * In Season Four, Earth was destroyed yet again by an event known as Praimfaya. However, Earth became habitable again in 2155.
 * Clarke and Madi are confirmed to be the only remaining humans outside on the surface, while many people are still in the Second Dawn Bunker and 7 other people are still in The Ark. Six years later, they manage to return safely on the ground.