The Bakersfield Expedition - S6-E13
Corrected entry: At the end of the episode Sheldon's sat nav voice asks "Can you name the four state capitals that are not served by the interstate system?" In fact, there are five, according to the Interstate System's website. Juneau, Alaska; Dover, Delaware; Jefferson City, Missouri; Carson City, Nevada; and Pierre, South Dakota.
Correction: Although there used to be 5 state capitals not served by the interstate system, the completion of I-580 means that Carson City is now served, hence there are only four, and the sat nav was correct. 580 was completed in 2012, the episode in question aired in 2013.
Shua320
What about Hawaii?
Honolulu, HI has an Interstate Highway. Not all Interstate Highways physically go from one state to another, the name just indicates it receives federal funding as part of the National System of Interstate and Defense Highways initially set up through the Federal Aid Highway Act.
Bishop73
Honolulu Hawaii is served by H1, H2 and H3, all part of the U.S. Interstate system.