Brilliant, Anita! The (war of) roses (white and red) were Lancester and York, so L = Lancaster.
Your prize is one of my favorites: https://m.youtube.com/watch?v=A1zyvlkhROU
PS: The German idiom for "mnemonic" is "Eselsbrücke", which literally translates to "donkey bridge".
What history donkey bridges did you learn in school?
To provide another example -
"753 (Sieben - Fünf - Drei) - Rom schlüpft aus dem Ei"
is a rhyme (Drei - Ei), literally translated "753 - Rome hatches from the egg", meaning Rome was founded (753 BC) .
"756 (Sieben - Fünf - Sechs) - Rom war ex" = "756 - Rome was ex" meaning the downfall of the Roman empire (756 AC).
Can you teach me American history mnemonics? Are there any in Lincoln?