  Major progress has been made in kaon physics in the past 50 years. The number
of KL->pi+pi- events has increased by 6 orders of magnitude, and the observed
CP violation was experimentally proven to be caused by a complex phase in the
CKM matrix. Recent kaon experiments are now searching for new physics beyond
the standard model with the K->pi nu nu-bar decays. The branching ratio of
K->pi nu nu-bar decays are 7-8 orders of magnitude smaller than the branching
ratio of KL->pi+ pi-.
  This paper reviews the progress of kaon experiments in the US and Japan, and
how the 6-7 orders of magnitude improvements were possible in the past 50
years.
