Complex sentence: Up until the 1940s the border had been open, without border controls; farmers at Grense Jakobselv, for instance, did not need to worry about whether or not their cattle were on the correct side of the border.
Split into simpler sentences: Up until the 1940s the border had been open, without border controls. For instance farmers at Grense Jakobselv did not need to worry about if their cattle were on the correct side of the border.