The link in the most recent comment by JohnInDC is one to a site with links to sites describing the U.S. Capitol. Whoever designed that link may not have known that the plan was  Ellicott's, rather than L'Enfant's. That also seems to be the case at Arlington Cemetery, where a historical marker in front of L'Enfant's grave illustrates Ellicott's Plan, rather than L'Enfant's original plan.  As L'Enfant objected to Ellicott's revisions in his letters, he would probably not be very happy about this misidentification. Fortunately, his grave is covered by a slab containing a copy of a portion of his own plan.  However, the public usually only sees the copy of Ellicott's plan (or revision). 

As to the caption of the pictures on the Wikipedia pages, the people who have commented above should all visit the website describing the Library of Congress' holdings of L'Enfant's and Ellicott's plans in the Library's catalog at http://lccn.loc.gov/95860578.   The summary of the holdings states:   “Summary: Includes plans by Pierre L'Enfant (facsimile maps published in 1887 by the U.S. Coast and Geodetic Survey) and Andrew Ellicott (1792) and … “.  

In its most definitive site, the Library of Congress therefore identifies the plan in the Wikipedia pages as Ellicott’s plan.  I will leave it to others to revise the caption on the plan in the Wikepedia pages, as I do not want to revise it again myself.