Lewis & Clark shipped west from St Louis MO.  Did they ever visit the
present day Louisiana?

Otisman --

Almost certainly they did not visit New Orleans together.  Meriweather
Lewis was at Fort Pickering (now Memphis, TN) on Sept. 15, 1809 --
then set out for Washington, DC via the Natchez Trace.  On Oct. 11 the
deeply depressed Lewis shot himself and died about 72 miles from
Nashville.  Nor had Lewis been to New Orleans before the expedition,
he being active in politics in Philadelphia and Washington, DC. 
Ambrose notes that Lewis specifically avoided returning via New
Orleans because of the value of the journals and maps -- and the fact
that British ships were routinely stopping American ships on the seas
and impressing Americans into service.

An excellent source for tracking Lewis & Clark and the events
surrounding their expedition is Stephen Ambrose?s book, ?Undaunted
Courage?.  This Amazon.com link actually allows you to read the book
online:
Amazon.com
?Undaunted Courage?
http://www.amazon.com/exec/obidos/ASIN/0684826976/qid=1108829824/sr=2-1/ref=pd_bbs_b_2_1/104-0810232-9416760

However, William Clark was in New Orleans before 1800.  He was in the
U.S. Army and in charge of detachments that were fighting Indians in
the early 1790s.  It was on the Fallen Timbers campaign in 1793-94
that he met Meriwether Lewis, who had just joined the Army.  The two
men spent 6 months serving together on that campaign, the only time
they spent together before the Lewis & Clark Expedition of 1803-1806.

Before leaving the Army, Lewis was sent on a mission to Natchez, where
he made friends with the Spanish governor, Gayoso de Lemos, according
to the Biography Resource Center?s ?Dictionary of American Biography,?
available at many public libraries.

De Lemos was so impressed by the red-headed Calrk that he granted him
a passport to visit New Orleans and he did sometime in the years
between 1797-1800.  Then in 1803, a letter from Capt. Lewis in
Washington came to him at his home in Clarksville, Indiana that would
involve him in the famous expedition.

After the expedition, Clark lived in St. Louis until his death, Sept.
1, 1838, with his activities likely taking him to New Orleans again. 
He was governor of the Missouri Territory in 1813 and in 1824-25 was
surveyor general for Illinois, Missouri and Arkansas.  In 1828 he laid
out the town of Paducah, KY.

Best regards,

Omnivorous-GA