File:Historical Map of the Coptic Dialects.png

Map sources:

• Coptic: A Grammar of Its Six Major Dialects by James Peter Allen
• The Coptic Encyclopedia, Volume 8 by Aziz Suryal Atiya
• The Rise of Coptic: Egyptian versus Greek in Late Antiquity by Jean-Luc Fournet

P.S:

• The Sahidic is Sahidic because it replaced Coptic dialects later in the Sahid region (Upper Egypt) as Arabic started to replace Coptic as the new spoken language and it was even called as the Egyptian Coptic as mentioned by the Coptic linguist Athanasius of Qus in the 14th century because it was the most common dialect knowing that after 11 centuries Coptic was abscent in Lower Egypt except for Boharic as liturgical dialect but Sahidic was still a spoken language in Upper Egypt for more centuries
• Aswanic dialect is considered a sub-dialect and is very close to Akhmimic, although, what makes it different is that "ϩ" is written before pronouns, meaning in normal Coptic it is said 'Afso', which means drank, but in the Aswanic dialect it is said 'Hafso'. It also has a distinctive way of writing; so the letter "ⲃ" is written instead of the letter "ϥ".
• Assyutic or a dialect close to it was spoken in the Kharga Oasis