For the record, let me quickly describe the steps we took to get to this data. You'll see why we may have missed a few agencies or why the list may still contain a few intruders. Also, if you do spot inadequacies - please take the time to inform us.
Firstly, we needed a list of all the U.S. digital marketing agencies. We took a bold assumption that SEO agencies need to
- Have a website (Right?!)
- Rank in Google Search (anywhere in the first 100 organic results/local results) for at least one of these terms in at least one of the 42K U.S. zip-codes:
- SEO agency
- Digital marketing agency
- SEO company
- PPC agency
- SEO services
- SEO consultant
- SEO expert
- Google Ads agency
- Have at least one of these terms in their homepage's <title> tag: SEO, Marketing, PPC, Ads, AdWords, Digital, SEM, Link-Building.
And so our Google Rank Tracker performed 341,000 searches (42K+ zip-codes x 8 search terms) and we ended up with 35 million search results belonging to 25,000 unique domains. Now we just had to filter them :) For that, we used Screaming Frog's Custom Search feature which helped us filter domains that had relevant keywords on their homepage's title tag.
Initially, we had around 13,200 websites left, but we still had to manually filter major SEO tools like Moz, Ahrefs, SEMrush, Raven, and others. Same goes for major SEO portals like SearchEngineJournal, SERoundTable, SearchEngineWatch, etc. Eventually, we were left with 13,105 SEO agencies.
Alas, we needed Ahrefs' Domain Rating to make the data even more interesting. This step was simple; our friends there were generous enough to send the data themselves.