Simply replace the unfilled areas such as "" and "[date]" with your information.
[Editors note: Letterwhiz.com doesn't necessarily condone the idea of proposing marriage with a letter. But if you think it's really for you...]
Dear [first name],
Today is our [#] anniversary together. We've shared so many good memories together. You are my best friend, and my partner in life, and I love you more now than ever.
It's amazing to see how we've grown together, the journeys we've taken, the places we've gone. We've had our ups and downs, but we've come through. We've survived. I love you with all my heart, and I want to ask if you will take my hand in marriage. Will you marry me?