The patron goddess of ancient Megara was Demeter, the goddess of agriculture, fertility, and the harvest. She was especially revered in the region due to the importance of agriculture in Megara's economy and daily life. Additionally, the city had a strong association with the worship of Demeter through various festivals and rituals dedicated to her.
Demeter is the goddess of fertility, and grain
I would assume the farmers of ancient Greece. Demeter was the goddess of crops, grain in particular.
Demeter was primarily associated with the city of Eleusis in ancient Greece. This city was the site of the Eleusinian Mysteries, which were sacred rites held in her honor, celebrating the cycle of life and agriculture. Demeter was revered as the goddess of agriculture, fertility, and the harvest, making Eleusis a significant center for her worship.
It could be Eleusina where the Eleusinian Mysteries, one of the most important religious event of Ancient Greece, took place in her honor.
The Greek goddess Demeter lived on Mount Olympus.
Megara worshiped many gods, having temples to Demeter, Artemis, Apollo, Aphrodite, and others.
The city-state for which Artemis was patron for was Sparta.
Athens was the city Athena is patron for. It was named after her.
Aphrodisias
Artemis is the patron goddess of the Hunt. She gives her aid to women in childbirth. She protects maidens and animals. She is the patron of the city Sparta.
Demeter is the Greek goddess of earth and harvest.