Here are some beginner chapter books:
Judy Moody
Magic Tree House
Junie B Jones
Mercy Watson
The Littles
Nate the Great
Here are some more book ideas for first graders: https://www.scholastic.com/parents/books-and-reading/book-lists-and-recommendations/series-characters-authors/popular-series-6-7-year-olds.html
“Step into chapter books” book list from Eugene Public Library: http://www.libraryaware.com/3338/NewsletterIssues/ViewIssue/f0629d38-00cd-47e5-90a5-1860eed65d2a?postId=225b4225-4d50-476c-89e3-32659c47aeab
Charlemagne First Grade 