According to this article, Americans stopped growing 50 years ago and have now been caught in height by the Japanese, which is startling:
In yet another blow to its global ego, the United States must now face the fact that it no longer grows the world's tallest people ... In a recent New Yorker article by Burkhard Bilger, "Why Europeans are getting taller  and Americans aren't." He found that after World War II the Dutch were, on average, four inches, or 10 centimeters, shorter than the average American ... The United States stopped growing in height around 1955, says Bilger, while the Dutch, the Germans and other Europeans were quietly putting on two centimeters per decade. Now even the Japanese have caught up with the Americans. The Northern Europeans, led by the Dutch, are now some three inches taller than average Americans.
http://www.iht.com/articles/2004/06/29/edjohnson_ed3__0.php
In yet another blow to its global ego, the United States must now face the fact that it no longer grows the world's tallest people ... In a recent New Yorker article by Burkhard Bilger, "Why Europeans are getting taller  and Americans aren't." He found that after World War II the Dutch were, on average, four inches, or 10 centimeters, shorter than the average American ... The United States stopped growing in height around 1955, says Bilger, while the Dutch, the Germans and other Europeans were quietly putting on two centimeters per decade. Now even the Japanese have caught up with the Americans. The Northern Europeans, led by the Dutch, are now some three inches taller than average Americans.
http://www.iht.com/articles/2004/06/29/edjohnson_ed3__0.php