What are the best tools for creating a Sitemap?

I am working on a mobile app and I have drawn a sitemap for it on paper. However, I want to to create a digital version of the sitemap. I have used Adobe Illustrator previously to create diagrams like this; however I have found that creating such diagrams on Illustrator is very time-consuming. I am looking for a faster way to create sitemaps.

I was wondering if anyone had any recommendations on any good free online tools for creating sitemaps? Any insights are appreciated.