Hassani Arab (Banu Hassan) emirate of the lower Senegal River / southwest Mauritania, formed in the Char Bouba war's aftermath; fought and allied by turns with Waalo, Futa Toro, and its sister emirate Brakna across the 18th century, controlling the gum arabic trade.
Conquered by the French under Xavier Coppolani during the pacification of Mauritania, dissolved in 1902 (per Wikidata) as the region was absorbed into French West Africa.
The atlas holds 5 border frames for Emirate of Trarza — the shape you scrub through changes in 1640 · 1680 · 1753 · 1799 · 1817.
Covers the precolonial Hassani emirates (Trarza, Brakna, Adrar, Tagant) of Mauritania in detail as part of the country's political history; no dedicated English-language monograph on Trarza alone was found verified, so this survey is used with a specific why per the polity-specific-first rule.