These icons () show footnotes as tooltips... for some browsers.
I-91 is mentioned in They Might Be Giants' "The End of the Tour", the last song off the "John Henry" album:
"Never to part since the day we met / Out on Interstate 91 / I was bent metal you were a flaming wreck / When we kissed at the overpass..."
6.02 miles ; from I-91 in Windsor to I-84 and I-384 in Manchester. Interstate 291 was to be a 26.4-mile, 270° beltway around Hartford; I-491 would handle the southeast route.
The Bissell Bridge over the Connecticut River opened in 1957, and was signed state route 291 until I-291 was constructed. I-291 completely opened on September 9, 1994.
For details, see I-291 at Connecticut Roads.
5.44 miles ; from I-91 to I-90 in Springfield. The freeway actually ends a few yards beyond, at Burnett Road. The two I-291's in Connecticut and Massachusetts are the closest (about 25 miles) of any identically numbered 3di's.
A 1953 highway plan by the state Department of Public Works outlines a Springfield Expressway easily recognizable as an ancestor of today's I-291, leading from a proposed US 5 expressway (now I-91) to a proposed US 20 (near where the Mass Pike runs today). There was also an outer belt planned, roughly along MA 21 from I-91 to I-90, that was never built. 
I-291 opened in the early 1970s. 
4.46 miles ; from I-91 in Springfield to near MA 116 in Holyoke.
An early ancestor of I-391 is part of a 1953 highway plan by the state Department of Public Works. The "major street with improvement" would have followed the MA 116 corridor in Chicopee. 
Possibly impacting Interstate 391's schedule was the 1980 theft of over 40 tons of steel from a 391 construction site.
I-491 (cancelled) Connecticut
Never completed, the 8.2-mile Interstate 491 freeway would have gone northeast from I-91 in Wethersfield to where I-84, I-384, and I-291 meet now. It would have covered the one quadrant (southeast) of the Hartford metro area not served by the proposed I-291.
For details, see I-491 at Connecticut Roads.
8.38 miles ; Interstate 691 connects I-91 in Meriden to I-84 in Southington. It's 6 lanes wide in downtown Meriden, 4 lanes otherwise. The oldest section, from US 5 to I-91, opened circa 1965; the newest, from CT 10 to I-84, opened in 1988.
For details, see I-691 at Connecticut Roads.