The Ravens logo is well known especially for anyone who lives in and around Baltimore.  The team itself was named after Edgar Allen Poe's poem "The Raven".  Not a lot of football teams have purple in their logo so the Raven's logo tends to be very memorable.  The logo that is currently being used was introduced in 1998 and has been in use ever since. The logo is both sharp in design and color which helps it to stand out.  A custom typeface was used for the logo and it matches the bird very well.

Info from - http://famouslogos.net/baltimore-ravens-logo/