In August 1972, a partnership agreement was signed in County Buildings, Linlithgow, by the Provost of Arnsberg from the Sauerland area of Germany, and the Convener for West Lothian County Council, Peter Walker.
This marked the foundation of the special relationship between the two areas, which is still going strong after 45 years.
To mark the special anniversary, 45 trees were planted at Tile Wood, which is near the Deer Farm at Beecraigs Country Park in the Bathgate Hills. This restores trees to a former wooded area of the park, with a special bench for visitors also installed.
The same number of trees were also recently planted at Brilon Wood in Hochsauerland to celebrate the friendship between the two areas.
Council Leader Lawrence Fitzpatrick said: "The twinning relationship between West Lothian and Germany's Hochsauerland has been very beneficial for residents from both areas.
"It's a great honour to help plant these trees to celebrate 45 years of twinning with Hochsauerland, and I hope the special relationship between our areas continues for many more years to come."
Liz Liddell, chair of the West Lothian Twinning Association, added: "During the last 45 years of twinning thousands of people, mostly youngsters, from both areas have travelled between the two countries enjoying the experience of meeting new people with different traditions and cultures and in many cases forming lasting friendships.
"Annually, scores of youngsters, students and adults are taking part in exchanges. These include musicians, sporting groups and teacher/study exchange opportunities to name but a few."