Yes, both Meriwether Lewis and William Clark were white.
Here can be found pictures of Meriwether Lewis:
http://www.mt.net/~rojomo/jpegslewsfthr.jpg
http://www.nps.gov/lecl/historyculture/imagesmeriwether-lewis-square_2.jpg
And here are pictures of William Clark:
http://upload.wikimedia.org/wikipedia/commons/e/e4William_Clark.jpg
http://xroads.virginia.edu/~CLASS/AM483_97/projects/hallwc.JPG