Final answer:
Northern Ireland was the part of Ireland that was partitioned by the Anglo-Irish.
Step-by-step explanation:
The part of Ireland that was partitioned by the Anglo-Irish is Northern Ireland. In 1921, the Anglo-Irish Treaty was signed, which resulted in the creation of the Irish Free State, encompassing the twenty-six southern counties of Ireland, while the six northern counties remained part of the United Kingdom, forming Northern Ireland. This partition was due to religious and political differences between the predominantly Protestant population in the north and the predominantly Catholic population in the south.