On the remote leaf of a chestnut tree, the morning dew comes together in a tiny drop of water, which falls onto a chestnut. The chestnut falls and rolls along the tree trunk, through a field of dandelions, and into a small crevice. In the path of the rolling chestnut is a yellow daisy, on which is a speck of dust. As the chestnut hits the daisy, the speck goes flying through the air, carrying the miniscule world of Whoville with it.
In the Jungle of Nool, Horton the Elephant hears a small noise, just a very faint yelp as if some tiny person were calling for help. He sees only a small speck of dust floating past through the air. He thinks that there must be one or more people on that speck. He wants to save them because "a person's a person, no matter how small". He catches it and places it on a very soft clover.
Horton talks with Ned, who is one of many very small people living in the town Who-ville on the speck; he is the mayor. Ned uses a sounding horn so that Horton can hear him. The people of Who-ville were not aware they are on a speck on a clover; Horton convinces Ned by demonstrating that he can put the speck into and out of the shade. Also, when the speck is put in a smelly place this can be observed, and shocks can be felt as earthquakes. Ned and his wife Sally have 96 daughters, and one son, Jojo, who does not say much. (Jojo was afraid that he would let down his father, Ned)
Ned is concerned about the safety of the town and tries to postpone the Who Centennial, but this is rejected by the Council. Horton and Ned agree that Horton has to find a safe place for the speck, and Horton plans to put it in a cave, on a sunflower, at the top of Mt. Nool.
