10-Year-Old Language and Cognitive Milestones. For many children, the development phase around 10 years old is packed with learning and rapid-paced cognitive growth. Right before your eyes, your child may seem to blossom from a little kid into a much bigger one with emerging critical thinking skills, huge advances in academic learning, a drive. Man o' War (March 29, 1917 – November 1, 1947) was an American Thoroughbred racehorse who is widely regarded as the greatest racehorse of all time. Several sports publications, including The Blood-Horse, Sports Illustrated, ESPN, and the Associated Press, voted Man o' War as the best American racehorse of the 20th century..