Jillis De Garmo was born in May 1703. He was the son of Frenchman Pierre De Garmo and Albany native Catharina Vandrheyden De Garmo. He grew up in a large family in several locations as his father struggled to make a living beyond the fur trade.

In January 1731, he married Rachel Evertson at the Albany Dutch church. By 1749, five children had been christened in Albany where he was an occasional baptism sponsor.

These De Garmos lived in the first ward where Jellis was listed among the qualified voters in 1742 and in 1763.

In October 1767, he obtained a lot from the city of Albany along the north side of Foxes Creek. It may have been called lot #15 and was bounded by Fox and Hare Streets and was between Hawk and Swan. In September 1768, the city council confirmed the deed and stated that the property was to be used as tanning pits.

In 1773, he purchased a lot of land near the Dutch church pastures from Anthony Hallenbeck. That year, he witnessed a will and was identified as a shoemaker.

He owned as many as seven pieces of property in the first and second wards. The assessment rolls for 1779 valued his lots and tan yard as well as his residence located near Court and Hudson Streets.

Jellis De Garmo filed a will in March 1779. It named his wife and son as heirs to his real and personal estate. Two years later, he was referred to as "Old D' Garmo" and had a Continental soldier living at his house. In 1788, his widow and son were listed on the first ward assessment roll. His will passed probate in 1796.