Longest Stretches of Interstates You've Still Not Traveled

[Big John]

I-90 from Cle Elum, WA to Tomah, WI.

[catch22]

I-10 from its intersection with I-75 in Florida all the way to its western terminus.

[Rothman]

Forgot to update I-5 from my San Diego trip some months ago...

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-5, I-205 to CA 76: 404 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-5, OR 99 to CA 120: 377 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles
I-55, I-270 to I-40, 262 miles

[TheHighwayMan3561]

I-95 south of Teaneck (have physically seen it from FL Turnpike, though)
I-5 from LA to Portland
I-15 from SLC to Butte
no meaningful independent sections of I-70 east of St. Louis, or I-64 for that matter
I-45

[Rothman]

Dear me, dear me, dear me...the I-55 one I mentioned last in my list is one I've chopped up as well.  Remaining longest segment is too small to list: 130 miles (I-270 to US 62 north of Sikeston).

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-5, I-205 to CA 76: 404 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-5, OR 99 to CA 120: 377 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles

[Ted$8roadFan]

Most interstates outside of New England.

[7/8]

My top 3:
1) I-35: From East Rundberg Lane, Austin, TX to I-80 in West Des Moines, IA (approx. 1464 km / 910 mi)
2) I-70: From Pena Blvd in Denver, CO to US 54 in Kingdom City, MO (approx. 1184 km / 736 mi)
3) I-80: From I-84 in Echo, UT to I-76 in Big Springs, NE (approx. 859 km / 534 mi)

[Rothman]

Eh, we'll add I-8, too...

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-5, I-205 to CA 76: 404 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-5, OR 99 to CA 120: 377 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles
I-8, Exit 89, Ocotillo to I-10, 265 miles