Chow and Lo mein are traditional dishes that stem from a single dish that is made with different ingredients due to geographic availability. In North China, the Mandarin area to be specific, there is an abundance of wheat and the food is much heartier because of the drastically colder weather. Because of these, the noodles are traditionally thicker and made of wheat, as opposed to the Cantonese Lo mein egg noodles in the south, where wheat is much less abundant.
Please refer to the Regional Differences page