Thank you for contacting us regarding your plant issues.  Typically in Ohio, tomatoes are susceptible to fungal diseases due to our high humidity during the summer months.  It is important that the plant was initially healthy when you put it in the ground. This symptom is commonly associated with fungal diseases like Early Blight, Septoria Leaf Spot, Fusarium Wilt and Verticillium Wilt. Early stages are sometimes challenging to tell apart, but many of the management practices are the same.  

Leaf Spot Diseases in the Garden, University of Delaware, is a resource to help narrow it down. https://www.udel.edu/academics/colleges/canr/cooperative-extension/fact-sheets/leaf-spots-tomatoes/ Or Colorado State is another good resource - https://extension.colostate.edu/topic-areas/yard-garden/recognizing-tomato-problems-2-949/

University of Minnesota has good, basic, instructions for management: https://extension.umn.edu/plant-diseases/tomato-leaf-spot-diseases

Ohio State offers a full fact sheet on growing tomatoes in the garden, and includes varieties that are disease resistant:https://ohioline.osu.edu/factsheet/HYG-1624

I believe it is Early Blight, but to be sure, University of Wisconsin has a an article with good photos to see the difference between Early Blight and Septoria Leaf Spot: https://cdn.shopify.com/s/files/1/0145/8808/4272/files/A2606.pdf