Official Sources of Mapping Information

[WeeeZer14]

NY/NJ/CT - http://www.nycroads.com/ Unofficial, but a wealth of knowledge

NJ - http://www.nj.gov/transportation/gis/ State DOT and GIS Maps

NY - http://www.nysgis.state.ny.us/ State GIS Maps

TN - http://tnmap.state.tn.us/viewer/ State GIS Maps
http://www.tdot.state.tn.us/maps.htm State DOT Maps
http://www.kgis.org/KGIS_Lite/MapViewer.html Knox County GIS

[vectorspace]

New Mexico

NM DOT: http://nmroads.com/

Albuquerque: http://www.cabq.gov/gis/

Rio Rancho: http://www.ci.rio-rancho.nm.us/index.aspx?NID=1312

[timl2k12]

Hillsborough County GIS, Florida. (County Seat Tampa)

[thom_p]

Tennessee: Hamilton County: http://maps.hamiltontn.gov/hcflex/

[Spil]

NY - http://www.nysgis.state.ny.us/ State GIS Maps

This has been updated to GIS.NY.Gov

And, wow, how bad is it when the state GIS maps have three road-name errors just within a block of my house? Hate to see how bad the rest of the state must be!

[OscarC]

Minnesota--
MN DOT Site:
- County Maps: http://www.dot.state.mn.us/maps/cadd/html/counties.html
- City Maps: http://www.dot.state.mn.us/maps/cadd/ht ... alpha.html
- Other (Metro maps, highways, traffic maps, etc): http://www.dot.state.mn.us/maps/index.html
- Construction maps: http://www.dot.state.mn.us/roadwork/current.html

Local government sites: http://www.state.mn.us/portal/mn/jsp/co ... Star&sp2=y

I've also used different sources of zip code boundary sites to help find some boundaries, especially in rural areas, but don't know about the copyrights or licensing on them so I won't post them.

[nnote]

http://maps.mcassessor.maricopa.gov/default.aspx
Central Arizona
Also AZ511.com for Highway info

[mwhead2]

Georgia
http://www.dot.state.ga.us/maps/Pages/default.aspx

Georgia County Parcel Maps
http://gaassessors.com/georgia-map.html

[marigolds]

State of Missouri spatial data clearinghouse:
http://msdis.missouri.edu/
This is the download link for every transportation file provided by the state:
ftp://msdis.missouri.edu/pub/state/transportation/st_trans06.e00.zip
But you are better off going here first and toggling on the transportation layers:
http://www.msdis.missouri.edu/data/themelist.html

They also have webservices:
http://msdis.missouri.edu/webservices/mapping/index.html
This is every road in the state cataloged by MoDOT as an ArcGIS REST endpoint:
http://msdisweb.missouri.edu/ArcGIS/rest/services/MoDOT_Roads_Quarterly_December_2012_WMS/MapServer
And as a KML generator REST endpoint:
http://msdisweb.missouri.edu/ArcGIS/rest/services/MoDOT_Roads_Quarterly_December_2012_WMS/MapServer/generatekml
These are ArcGIS REST endpoints for every quarterly updated of the roads layers:
http://msdisweb.missouri.edu/ArcGIS/rest/services/MSDIS_Download/MapServer/182

[mapcat]

Although, not really an official source of mapping information, I recently came across this site: http://www.fhwa.dot.gov/trafficinfo/index.htm (National Traffic and Road Closure Information). It provides links to a bunch of sources (including links to all the state DOTs) that I find useful in addressing some URs.

Thanks. Added.