Robert C. Winthrop gave an address at the laying of the cornerstone for this structure in 1848. The original design by Robert Mills featured a colonnade, but it was never built due to cost. This structure was delayed by costs and the Civil War for over 25 years until its completion in 1885. For 10 points, name this obelisk located in Washington D.C., east of the Reflecting Pool.
a) Washington Monument
b) Lincoln Memorial
c) Jefferson Memorial
d) Martin Luther King Jr. Memorial