Answer: Find that monument!

Quick answers: The sculpture in the teardrop-shaped traffic island is for John Ericsson, the Swedish inventor of the Monitor (an ironclad fighting ship in the US Civil War), the twin screw propeller system, and one of the first torpedoes. 

Quick extra credit answer:  The sculptor of his monument was James Earle Fraser, a prominent sculptor of the time who ALSO designed the Navy Cross, the highest ranking medal in the Navy. 

John Ericsson, inventor of the Monitor
and much else (image courtesy of Wikimedia)

As most readers pointed out, the easiest path to solving this was to:

1. Find the teardrop-shaped traffic island near the Lincoln Memorial.  I used Google Maps to do this, searching first for [Lincoln Memorial Washington DC] and then quickly scanning the map.  The teardrop traffic island more-or-less leaps out at you off the page.  (Link to map.) 

2. Zoom in on the island and see the label popup identifying this as the “John Ericsson National Memorial.”  That led me to search for [John Ericsson] and thence to the Wikipedia (and several other) articles about him. 

3. To puzzle out the “Navy medal” I first searched for [Navy highest medal] and learned it was the Navy Cross.  Then, a quick search for
["Navy Cross" John Ericsson] led me to multiple articles about James Earle Fraser, the man who sculpted them both.  (I quoted "Navy cross" because I wanted that particular 2-word phrase, and not an accidental co-occurrence near each other.)  

James Earl Fraser (image courtesy Wikimedia)

As several readers pointed out, Fraser also sculpted the buffalo nickel, a coin that numismatists know well.

This wasn’t that difficult of a problem (although note that I once again changed the image to be visually recognizable, but not useful in Search-by-Image).  And it’s interesting to note how many people recognized the deck of the Monitor straight away.  I’m going to have to come up with some more challenging tasks for you folks! 

Search lessons: (1) Visual recognition helps a great deal in doing searches for things described as "teardrop-shaped."  You might get lucky searched for such a phrase, but don't count on it.  

(2) When searching for associations between things (such as between the the Ericsson memorial and the Navy Cross), it's often best to put in just the two things you're looking for and let Google do the heavy lifting.  I COULD have tried to guess that it was the sculptor who was the connecting idea, but if that wasn't right, I might have wasted a lot of time checking down dead-ends.  If you just put the two ideas side-by-side in a query, Google will automatically search for the relationship for you.  

If you have a few moments, it's worth reading about Ericsson, who was a remarkable polymath and inventor during the mid-1800s.  His engineering work and life in general are remarkable.  He not only designed and built the Monitor, but also the pivoting gun turret (still in use in modern warships), a kind of external-combustion engine that competes with the Stirling engine, electrically run torpedoes... it goes on and on. 

Search on!