The word "capital" in "capital punishment" refers to a person's head. In the past, people were often executed by severing their head from their body.
As of 2000-OCT-19, during the last decade of the 20th century, 547 prisoners have been executed in the United States -- one third of them in Texas. Another 3,500 wait on death rows. None have been executed in Canada; that country abolished the death punishment decades ago.
The United States is one of the very few industrialised countries in the world which executes criminals. It is one of the few countries in the world which executes mentally ill persons, persons with very low IQ, and child murderers (i.e. persons who were under 18 at the time of their crime).