What phrase does the little blue engine repeat in 'The Little Engine That Could'?

In “The Little Engine That Could,” the little blue engine repeats, “I think I can.” The phrase expresses the story’s central lesson: determination and optimism can help overcome a difficult challenge. In the familiar plot, a stranded train loaded with toys and other goods needs to cross a mountain after larger engines refuse to help.

The small engine agrees to try, even though it has never pulled such a heavy train over the mountain. As the climb becomes harder, the engine keeps saying, “I think I can,” while steadily pulling the cars upward. After reaching the top and descending safely, the wording changes to “I thought I could,” marking the successful conclusion.

The tale existed in several forms before the best-known book version. An early printed version appeared in 1906, while the title “The Little Engine That Could” was used in the 1920 My Book House series. The widely known Arnold Munk version, published under the pen name Watty Piper, appeared in 1930. Some adaptations alter the engine’s color or details, but “I think I can” remains the canonical phrase.