Who said "I have learned that strength is often quiet and humble."?

This quote is attributed to Carl Sandburg.

I have learned that strength is often quiet and humble. - Carl Sandburg

"I have learned that strength is often quiet and humble."

Carl Sandburg Strength

Poet American 1878–1967

"I am the people—the mob—the crowd—the mass."

"Life is like an onion; you peel off one layer at a time and sometimes you weep."

"Nothing happens unless first we dream."

"I have always been ahead of my time."

"Strength comes from within."

"A woman should be proud of who she is."

"A strong woman can overcome anything."

"The only thing I'm good at is killing."