Eastern Chou Dynasty
People call the first three hundred years of the Eastern Chou period the Spring and Autumn period because it was a good time for China. Tool-makers in China learned how to use iron to make tools at this time; they probably learned from iron-workers in West Asia, maybe by way of India or Central Asia.
But iron also made good weapons, and the 200 little states began to fight each other all the time. The period from 481 to 221 BC is called the Warring States period. By about 300 BC, there were only seven big states left. By 256 BC, the Chou emperors lost power, and the only rulers of China were the kings of the seven states. These kings fought among themselves until the king of Ch'in, the strongest state, succeeded in making himself emperor and established the Ch'in Dynasty.
To find out more about the Chou dynasty in China, check out these books from Amazon.com or from your library:
Eyewitness: Ancient China, by Arthur Cotterell, Alan Hills, and Geoff Brightling (2000). For kids, with lots of excellent pictures.
China (History of Nations), by Greenhaven Press (2002). For middle schoolers. The negative review on Amazon is actually for a different book - don't be alarmed!
Cambridge History of Ancient China : From the Origins of Civilization
to 221 BC, by Michael Loewe and Edward L. Shaughnessy (1999). A more
challenging read, and much more expensive, but it has all the good solid
reliable information you could want.