Dear Jay, 

Thanks for reaching out; your site looks beautiful! Here are two grasses that you may wish to consider: 

1. Indian grass (Sorghastrum nutans), grows 3-6' tall, suited for your zone:  https://open.lib.umn.edu/nativegrasses/chapter/3-14-indiangrass-sorghastrum-nutans/

2. Switchgrass (Panicum virgatum), grows 3-6' tall, suited for your zone: https://open.lib.umn.edu/nativegrasses/chapter/3-12-switchgrass-panicum-virgatum/ I will note that switchgrass can be aggressive, but it can also be beautiful in the fall (https://extension.umn.edu/yard-and-garden-news/five-native-grasses-great-fall-color)

Since you wish to start from seed, it may take 2-5 years for the plants to reach full size. Here is a helpful UMN Extension article with more information on planting and maintaining prairie grasses: https://extension.umn.edu/planting-and-growing-guides/planting-and-maintaining-prairie-garden#common-prairie-plants-1644213

Good luck!