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The highest numbered US route was US 830, which followed the Columbia River on the Washington side from US 97 to US 101. Parts of it now exist as WA 4 and WA 14.
35.51 miles ; loops west of Jacksonville. FL 9A, which loops around the city to the east, will eventually be part of a full 360-degree I-295, when the last remaining segments are completed in 2006.  The I-295 designation will be applied to FL 9A when construction is complete.  
The Dame Point Bridge, on the east loop, has a 1300-foot cable-stayed span, which was in 1990 the second longest in the world.
A proposed FL 9B spur leading south from FL 9A to I-95 may become I-795.
I-295 Washington, D. C.; Maryland
8.05 miles ; From I-495 east of the Potomac to I-395. The remaining portion of I-295 in Washington is marked DC 295, the only current District of Columbia numbered highway. You can follow this highway to Baltimore, though it changes identities several times: I-295, DC 295, the Baltimore - Washington Parkway (no number), then MD 295. 
It might have been easier to follow had the District's April 1958 proposal been approved: Interstate 63 for I-295, and I-63N for proposed I-695. AASHTO flatly denied this proposal.  (And no, Marion Berry was not yet in office.)
AASHTO's counteroffer for I-63 was I-195 (perhaps D. C. officials came up with it). In July 1958, reasoning that the highway was more part of a loop than a spur, D. C. requested I-295, which was granted. 
I-295 Massachusetts; Rhode Island
26.58 miles ; Providence beltway, from I-95 near Warwick, R. I. to I-95 near Attleboro, Mass. It was completed in 1969.
Proposed eastern half renumbered to 895; never constructed
Interstate 895 was never constructed, but there is evidence at the I-95/295 half-cloverleaf interchange in Massachusetts that the 295 roadway was intended to continue.
About 52 miles long, I-295 leads from I-95 south of Portland to I-95 at Gardiner. Formerly 11.02 miles long, I-295 was extended as part of a January 2004 changeover where route numbers and exit numbers were changed to make area highways easier to navigate. 
Original route: 11-mile Portland loop
Originally, I-295's northern terminus was the Falmouth Spur; I-95 took over from there, leading to Brunswick and then Augusta. The north half of the original I-295 dates back to at least 1965. The entire 11 miles was apparently completed in 1978. 
MDOT's effort to unclutter, clarify Turnpike numbers, exits
In 1999, state and turnpike officials began discussing how to clear up motorist and tourist confusion over Maine Turnpike route and exit numbering. 
For historical reasons, exit numbers were sequential instead of milepost-based, which is generally regarded as more useful. (There's some discussion at my Exits in Connecticut page.) Even worse, exit numbering along I-95 northbound restarted at York, several miles into Maine, where the Turnpike began.
Route numbers didn't follow physical highways, either. I-95 followed part of the Turnpike north of the Portland I-295 split, but then crossed over the Falmouth Spur to take over the Portland-Brunswick route that I-295 had started. Meanwhile, the Turnpike north of the Spur suddenly became I-495.
The Maine DOT and the Maine Turnpike Authority decided to establish the following in early 2004:
Exit renumbering fallout affects businesses
A number of Maine businesses with location-specific names will probably have to change them: for example, "Exit 3 Safe Storage" will be located at exit 25, and "Exit 32 Automotive" will be at exit 120. 
I-295 New York
9.10 miles ; from I-678 in the Bronx, across the Throgs Neck Bridge, to the Grand Central Parkway in Queens. The expressway itself was completed in 1963. Once part of I-78, the Clearview Expressway became I-295 around 1974 .
A 6.3-mile, $194M extension south to the Nassau Parkway was proposed in 1970. 
I-295 New Jersey; Delaware
73.77 miles ; from I-95 north of Trenton to I-95 south of Wilmington. The section between US 322 and NJ 73 (Camden) dates back to 1965 or earlier. The Trenton area was finished last, the section between US 130 and I-195 opening in 1995 .
Pennsylvania is planning a connection between the Turnpike (I-276) and I-95, two freeways that currently cross without access ramps. The expected completion date is 2012. An early plan was to extend the I-295 designation into Pennsylvania, to take over from I-95, which would cross into New Jersey using the Pa. Turnpike. However, in a 2005 agreement between the states, I-195 will be extended around Trenton into Pennsylvania instead.
I-295 (proposed) North Carolina
This is the Fayetteville Outer Loop, a planned 40-mile highway serving Fayetteville. It will start at I-95 and US 13 in Eastover and end at I-95 in Robeson County. 
The loop was approved by the state DOT in January 2002. A ribbon cutting was held June 16, 2003 on the start of a segment connecting US 401 and River Road. Parts of this highway at US 13 should open in 2005. 
A cost estimate for the entire loop is $350 million, and everything might be open by 2020. 
In 2003, NCDOT proposed the number I-195 for this loop, described at the time as being 35.18 miles. This was rejected by AASHTO, possibly because the leading odd digit ("1") denotes a spur, not a loop. 
52.56 miles ; eastern bypass of Richmond and Petersburg.
Interstate 295 was originally envisioned as part of a beltway around Richmond only, and was included in Virginia's original interstate system. The interstate portion would extend from I-64 west of the city, clockwise to just beyond I-95 to the south. By 1969, a state freeway (VA 288) was planned to complete the loop, from I-95 in the south to I-64 in the west. 
The portion of the route between VA 5 and I-95 would have impacted the Richmond National Battlefield parkline, and was eventually abandoned. In 1978, the state received FHWA approval to reroute and extend the south end of I-295 about 20 miles, to provide an eastern bypass of Petersburg as well.
The 25-mile north half of I-295 opened in 1980 and 1981; the southern half opened in stages starting in 1988, and was completed in June 1992.  To allay concerns over induced sprawl, three interchanges were removed from the southern section; between US 60 and I-95 to the south, interchanges are about 6 miles apart. 
I-295 crosses the James River on the Varina-Enon cable-stayed bridge, a six-lane, 150-foot-high span that opened in 1990. 
So far, the highway is primarily surrounded by trees and quite scenic. All interchanges are cloverleaves, except for the higher-capacity interchange at its northern terminus at I-95.