A few mythical stories related with Rath Yatra's origins exist that reflect the socio-religious thinking and beliefs of the people of the region. Some of the chief ones are:
To kill Lord Krishna and Balram, Kansa, their maternal uncle, invited them to Mathura. He sent Akrur with a chariot to Gokul. As asked, Lord Krishna, along with Balram, sat on the chariot and left for Mathura. The devotees celebrate this day of departure as Rath Yatra.
Euphoric devotees celebrated the day when Lord Krishna, aftr defeating the evil Kansa, gave them darshan in Mathura in a chariot with his brother, Balaram.
Devotees in Dwarika celebrated the day when Lord Krishna, accompanied by Balaram, took Subhadra -- his sister, for a ride on a chariot to show the city's splendor.
Once Lord Krishna's queens requested mother Rohini to narrate the many interesting amorous episodes (ras lilas) of Lord Krishna with the Gopis. Rohini--considering it improper of Subhadra to hear such episodes (Leela)--sent her away. Still, the Vrajkatha soon absorbed Subhadra along with Krishna and Balram, who by now had appeared on the scene. While they were completely engrossed with the stories arrived Narad. On finding the siblings standing together motionless, he prayed, "May the three of you grant darshan in this manner forever." The boon was granted. And the three forever reside in the Puri Temple of the Lord Jagannath.
There is an exciting story of Lord Krishna becoming the Sarathi - driver of Arjuna's chariot, during the 18-day battle of the Mahabharata.
Finally, a story which has been passed on from mouth to mouth, tells what happened after the cremation of Lord Krishna's mortal body.
When Shri Krishna was being cremated in Dwarika, Balaram, much saddened with the development, rushed out to drown himself into ocean with Krishna's partially cremated body. He was followed by Subhadra. At the same time, on the eastern shore of India, King Indradyumna of Jagannath Puri dreamt that the Lord's body would float up to the Puri's shores. He should build a massive statue in the city and sanctify the wooden statues of Krishna, Balaram and Subhadra.
The bones (asthi) of Lord Krishna's body should be put in the hollow in the statue's back. The dream came true. The king found the splinters of bone (asthi) and took them. But the question was who would carve the statues. It is believed that the Gods' architect, Vishwakarma, arrived as an old carpenter. He made it clear that while carving the statues nobody should disturb him, and in case anybody did, he would vanish leaving the work unfinished.
Some months passed. The impatient Indradyumna opened the door of Vishwakarma's room. Vishwakarma disappeared immediately as he had warned before. Despite the unfinished statues, the king sanctified them; placing Lord Krishna's holy cinders in the hollow of the statue and installed them in the temple.
A majestic procession is carried out with the statues of Lord Krishna, Balaram and Subhadra, every year, in three gigantic chariots. The huge chariots are pulled by devotees from Janakpur to the temple in Jagannath Puri. The statues are changed every 12 years--the new ones being incomplete also.
The Jagannath Puri Temple is one of the four most sacred temples in the four directions of the India--the other three being: Rameshwar in South, Dwarka in West and Badrinath in the Himalayas. Maybe, the temple in Jagannath Puri is the world's only temple with the statues of three deities who are siblings -- Lord Krishna, Balaram and Subhadra.