Google Books and the Internet Archive have a selection of the Proceedings of the Board of Supervisors of the County of Niagara books digitized online for free for the following years:

1891: https://www.google.com/books/edition/_/DSItAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEBw

1910: https://archive.org/details/proceedingsofboa1910niag

1911: https://www.google.com/books/edition/_/V_5FAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEEA

1912: https://www.google.com/books/edition/_/5iEtAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEEo

1913: https://www.google.com/books/edition/_/Ti4tAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEDI

1915: https://www.google.com/books/edition/_/8ZxGAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDECE

1916: https://www.google.com/books/edition/_/AkItAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDECY

1917: https://www.google.com/books/edition/_/JT8tAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEDw

1918: https://www.google.com/books/edition/_/Yz8tAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEC4

1919: https://www.google.com/books/edition/_/X0AtAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEDc

1921: https://www.google.com/books/edition/_/YUAtAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEEU

1922: https://www.google.com/books/edition/_/vUAtAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDECo

1923: https://www.google.com/books/edition/_/30ItAQAAMAAJ?hl=en&sa=X&ved=2ahUKEwjKtKP_pqfvAhVyFFkFHQmwAp8Qre8FMAB6BAgDEBc