The unnamed island located far North-East of Ohara, from where departed a boat on which Nico Robin was spotted by the marines after fleeing Ohara, which confirmed her survival and resulted in her first bounty being issued.
52 years ago before the current timeline, as the Rumbar Pirates, led by "Calico" Yorki, were sailing the West Blue, they came across a baby whale that was lost. Seeing that the whale was crying, Brook, a member of Yorki's crew, suggested that they cheer the whale up with some music. Having cheered the young whale up, Laboon, as Brook had named him, began following the Rumbar Pirates through their adventures.
As the crew drew nearer to the Grand Line however, Yorki and some of the other Rumbar Pirates asked Brook to convince Laboon to stay in the West Blue since he was the closest to the whale, but Laboon still followed them all the way to the other side of Reverse Mountain. Seeing that the Grand Line was just too dangerous for a young whale, Yorki asked Crocus, an inhabitant of Reverse Mountain, to take care of Laboon while they ventured through the Grand Line. As Yorki and his crew left Laboon in Crocus's care, they promised to return someday in two to three years and take Laboon back with them.
However, Yorki and some of the other Rumbar Pirates eventually contracted an incurable disease. In order to save the rest of the crew, Yorki decided to take himself and the other infected members, and escape the Grand Line through the Calm Belt. Brook, now Captain of the Rumbar Pirates, and his remaining crewmates were then attacked by some enemy pirates at the Florian Triangle. A good number of the crew survived the attack, albeit barely, but since the enemy had tainted their weapons with poison and the Rumbar Pirates' doctor was killed in the attack, the survivors were slowly dying. The remaining Rumbar Pirates slowly succumbed to the poison and died one after another while recording their last song in a Tone Dial so that Brook, who had eaten the Yomi Yomi no Mi, would be able to bring it for Laboon to hear after resurrecting. Brook continued playing alone until he too succumbed to the poison and died. After a year of searching, the soul of Brook found the Rumbar Pirates' ship and his body, which had decomposed to bones. Resurrected as a skeleton, Brook put his comrades' remains in coffins. However, Brook remained ever aware of his crew's inability to keep their promise to Laboon.
50 years later, the remains of the Rumbar Pirates were buried at Thriller Bark, a giant ship that came from the West Blue and was now located at the Florian Triangle.
Until 22 years ago, Ohara Island held the Tree of Knowledge, a famous place where the books recording the events of history were held.
Inside the tree, the world's best archaeologists resided, studying the events of history and making sure the words held in each book were not forgotten. It was their duty to protect and preserve the books and their record of time. 22 years ago before current time, they dared to do the unthinkable and began to study a period known as the Void Century, a period in history roughly 800 years ago that the World Government banned from researching.
When word got out about what they were researching, the island was ordered to be destroyed using the "Buster Call". During the Buster Call, some quick thinking on the archaeologists' part saved the books inside the tree from being lost. They threw them into the lake outside, safe from the fire of the Buster Call that tried to destroy them.
Only one person survived the massacre of Ohara: a young girl named Nico Robin. Her knowledge of the Poneglyph language meant that she was the only one who could learn the banned history and possibly revive the Ancient Weapons, artifacts of war with the potential to destroy the world. This led to her being branded as a "Devil Child" by the World Government, being chased and persecuted until the present, as a member of the Straw Hat Pirates.
Capone Bege and the Five Great Families of the West
Capone Bege, at some point of his life, became the boss of one of the Five Families of the West, the biggest mafia organizations that controlled most of the West Blue's Underworld operations. He quickly became infamous due to quickly bringing down rival mafias by going directly for the heads of their bosses. However, he only stole money and precious items from the organizations he brought down, being content to watch the struggle for power that would ensue afterwards without gaining any power or territory of his own. Bege accumulated many enemies, but managed to repel all of them with his Devil Fruit powers.
Bege finally grew bored with his dominance and sailed to the Grand Line as a pirate; however, his methods did not change, as he targeted renowned pirate captains while leaving their crews intact. He is also still pursued by people seeking revenge for his actions to this very day.
The West Blue is so far the only sea to have no known members of the D. Family.