It's better as "In the past, the only transport in the Arctic was sledges"

Thanks

I'd say: In the past, sledges were the only transport in the Arctic. This follows the basic English word order of "Time + Subject + Verb + Place. For more info, check out: http://moodle.usm.md/moodle/pluginfile.php/18500/mod_resource/content/1/word-order-in-english.pdf