A post by US Sen. Chris McDaniel claims that "Robert E. Lee was the most decorated soldier in the US Army." (That technically goes to Audie Murphy overall, but let's just look at it as of Lee's resignation in April 1861.) I have looked around, but haven't located any information about Lee's ribbons, medals, or other decorations at that time.
What decorations did he have? How did that compare with others who served in the Mexican-American War? Were there others with more?
None. The senator was mistaken.
Medals for valor were not introduced into the US military until the Civil War (north and south). Campaign medals were not introduced until the Spanish American War. (Civil War and Indian Campaign Medals were authorized in 1907, well after the events in question.) Medals that recognize non-combat service are also a 20th century innovation.