Interstate 66
interstate highway in the United States
Interstate 66 (I-66) is a 76.32 mile east–west interstate highway in the eastern United States. The highway runs from an interchange with I-81 near Middletown, Virginia, on its western end to an interchange with U.S. Route 29 (US 29) in Washington, D.C., at the eastern terminus. The route parallels State Route 55 (SR 55) from its western terminus at I-81 to Gainesville, Virginia, and US 29 from Gainesville to its eastern terminus in Washington. I-66 is unrelated to US 66, which was located in the Midwest-West region of the United States.
The E Street Expressway is a spur from I-66 into the Foggy Bottom neighborhood of Washington, D.C.
Planned expansions of I-66, including an auxiliary route, I-266, were ended by community opposition in the 1970s. I-266 would have begun in Arlington, Virginia, and terminated in Washington at K Street NW.
Route description
Virginia
Interstate 81 to Dunn Loring
I-66 begins at a directional T interchange with I-81 near Middletown, Virginia. It heads east as a four-lane freeway and meets US 522/US 340 at a partial cloverleaf interchange. The two routes head south to Front Royal and north to Lake Frederick. I-66 continues east and crosses the Blue Ridge at Manassas Gap, paralleling SR 55 (John Marshall Highway) and meeting US 17 at a partial interchange with no access from eastbound I-66 to northbound US 17. SR 55 also merges onto the freeway at this interchange, forming a three-way concurrency that ends near Marshall, with SR 55 leaving along with U.S. Route 17 Business (US 17 Bus.) at a diamond interchange and US 17 leaving at the next exit, also at a diamond interchange.
The public source identifies “Interstate 66” as interstate highway in the United States. This brief keeps that definition visible, then builds a research path around Interstate, interstate and highway.
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A short description can identify a subject without explaining its stakes. For “Interstate 66”, the useful work is to connect “interstate highway in the United States” to the records capable of establishing context and consequence.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 27, 2026. The linked authority identifier is Q94600. The Library of Congress control number is sh86006341. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Interstate 66” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.