Tahmoor is a small town in the Macarthur Region of New South Wales, Australia, in Wollondilly Shire. Originally named Myrtle Creek, it was …Tahmoor is a small town in the Macarthur Region of New South Wales, Australia, in Wollondilly Shire. Originally named Myrtle Creek, it was a farming area on the Great Southern Road, later named the Hume Highway.