Have you come across [Local Harvest](https://www.localharvest.org) before? That might be a good data source, at least for what farms exist where. I don't know if they collect data on what farms actually grow.

But I empathize a lot. I've pursued a number of side projects in this space. I've worked on an online farmer's market, a plant database, and a recipe database in the hope of solving a nexus of problems around eating sustainably and sourcing food locally. The only one that ever actually made it to live was http://www.fridgetofood.com and I haven't touched that in years, so it has decayed pretty hard.

I always got hung up on the data collection and translation aspect of things. It's not an easy problem to solve.