In case the above University of Minnesota link goes dead (it's an old link) here are the data in CSV format:

state1,state2,length
AL,FL,196.1
AL,GA,291.3
AL,MS,323.9
AL,TN,146.7
AR,LA,166.5
AR,MO,325.3
AR,MS,282.8
AR,OK,198.2
AR,TN,125.1
AR,TX,65
AZ,CA,198.4
AZ,CO,0
AZ,NM,391
AZ,NV,181.4
AZ,UT,275.8
CA,NV,608.2
CA,OR,216.3
CO,KS,207.7
CO,NE,173.2
CO,NM,333
CO,OK,52.9
CO,UT,276.1
CO,WY,260.2
CT,MA,86.5
CT,NY,82.3
CT,RI,40.3
DC,MD,24.6
DC,VA,1.9
DE,MD,122
DE,NJ,1.4
DE,PA,22.6
FL,GA,261.4
GA,NC,68.6
GA,SC,249.6
GA,TN,72.6
IA,MN,262.1
IA,MO,235
IA,NE,148.9
IA,SD,85.6
IA,WI,86.7
ID,MT,569.8
ID,NV,153
ID,OR,305.8
ID,UT,153.6
ID,WA,210.3
ID,WY,170.7
IL,IA,200.5
IL,IN,295.5
IL,KY,122.4
IL,MO,331.6
IL,WI,144.4
IN,KY,296
IN,MI,108.4
IN,OH,178.8
KS,MO,307.5
KS,NE,356.5
KS,OK,409.1
KY,MO,59.8
KY,OH,155.5
KY,TN,338.5
KY,VA,119
KY,WV,79.1
LA,MS,456.6
LA,TX,222.7
MA,NH,86.7
MA,NY,49.4
MA,RI,62.6
MA,VT,40.9
MD,PA,195.7
MD,VA,253.7
MD,WV,174
ME,NH,159.3
MI,OH,69.7
MI,WI,205.1
MN,ND,217.1
MN,SD,180.8
MN,WI,291.1
MO,NE,53.6
MO,OK,34.4
MO,TN,60.9
MS,TN,119.2
MT,ND,210.8
MT,SD,65.3
MT,WY,377.7
NC,SC,312.2
NC,TN,218.9
NC,VA,327.7
ND,SD,359
NE,SD,399.4
NE,WY,138
NH,VT,180
NJ,NY,103.4
NJ,PA,150.9
NM,OK,34.5
NM,TX,536.2
NM,UT,0
NV,OR,152.5
NV,UT,344.6
NY,PA,306.1
NY,VT,80.3
OH,PA,92.4
OH,WV,243.5
OK,TX,715.4
OR,WA,385.8
PA,WV,118.6
SD,WY,137.7
TN,VA,110.7
UT,WY,173.1
VA,WV,381.2