St. Charles starting point?

Does anyone have any information regarding traveling from St. Louis to St. Charles to start our ride on the Katy Trail? How far of a ride is it from St. Louis to the trail head at St. Charles? Any information would be greatly appreciated. Thanks. Scott

Are you wanting to start in Downtown St. Louis at the Arch or do you have a different starting point in mind? Would you rather bike along the Mississippi River for most of that distance out to St. Charles or do you want to ride through the heart of St. Louis where you can see some of the nice neighborhoods?

The Mississippi Riverfront Greenway Trail runs about 12 miles north from Downtown St. Louis if you are starting near the Arch. Your best be then is to enjoy the longer route across the Mississippi River and utilize the nice trails in Illinois in order to get to Machens. This Illinois route is about 28 miles versus 18 miles, but the shorter Missouri route would require you to ride on major highways with small shoulders. The Illinois route takes you across the Old Chain of Rocks pedestrian/bike bridge into Illinois where you jump on the Madison County Confluence Trail.
Here is the route that I posted several weeks ago along the Mississippi River up to Machens:

Take that trail to the northwest past Wood River and into Alton where you can cross back into Missouri using the striped bike lane on the cable-stayed Clark Bridge Hwy. 67). Once you cross back into Missouri, take rough West Alton Trail to get close to St. Charles Street. Then take St. Charles Street to 94 Hwy. to Saale Road to Dwiggins Road to 94 Hwy. to Machens Road...the idea is to use county sidestreets to stay off of 94 Hwy. as much as possible. Machens Road takes you to the Katy trailhead just across the live railroad tracks.

Weldon Spring to Downtown St. Louis (Part 1):

I really enjoyed the route that I took this October from the Katy Trail to Downtown St. Louis. I really enjoyed rolling into downtown one hour before the Cubs/Cardinals game...here is the route:
Take the Route 364 (Page Avenue Bridge) across the Missouri River from the Katy Trail.
Follow the signs to follow the Creve Coeur Connector Trail.
When you dive down the hill away from the highway into Creve Coeur Park, continue straight through the bike roundabout and go past the Lakehouse (a great place to stop if you want to eat a whole meal or to just grab a Gatorade).
Continue straight on the trail until it parallels Creve Coeur Mill Road and turns into a sidewalk.
Continue straight on the sidewalk for about 500' past the apartment complex where the sidewalk turns into a crushed gravel path that turns left along a creek and utility easement.
The gravel path connects to the Old Farm Estates pool parking lot and playground where you can then connect to Bookbinder Drive.
Turn right onto Bookbinder Drive and enjoy a couple of big hills with fairly light traffic (especially compared to Creve Coeur Mill Road).
Bookbinder eventually runs into Creve Coeur Mill Road, but you only have to ride about 100' on it until you link up with Olive Boulevard.
Olive Boulevard is a road with heavy traffic, but it has a mix of wide bike shoulders, striped bike lanes, and sidewalk areas. Along Olive, the single point interchange at I-270 and the cloverleaf interchange at Lindbergh (Hwy. 67) are the only difficult parts.
Once you get past Lindbergh, continue straight on Olive for about 1/2 mile past Warson and Old Bonhomme, then turn right at the next street Newcastle.
Go down the hill on Newcastle for about 1/4 mile and you will see an asphalt bike trail begin along the left side of the roadway (this is an awesome paved trail through Olivette).

Part 2:

The 1/2 mile trail connects to Dielman Road where there is a signed bike route from Dielman to Hill/Dale to Elkington to Villa Avenue.
From Villa Avenue, turn right onto Price Road, go up the hill and turn left onto Old Bonhomme Road.
Take Old Bonhomme Road for 1/4 mile over the I-170 bridge where you will immediately turn left and go down the hill onto the Centennial Greenway Trail system.
Take the Centennial Greenway Trail for 2 miles straight south until it dead-ends at Shaw Park.
Work your way through Shaw Park past the tennis courts and past the swimming pool.
Cross Brentwood Boulevard at Carondolet Avenue and stay straight on Carondolet for 1/2 mile (you ride on a nice wide street and cut through the County Courthouse area that has wide walkways).
Carondolet Avenue dead-ends at Carondolet Plaza, but go right around the plaza roundabout and you will see a bike/ped bridge over Forest Park Parkway.
Once you cross the ped bridge, stay to the left and ride down Edgewood Drive where you will turn left onto Wydown Boulevard.
Wydown Boulevard has great bike lanes and nice tree lined streets as it leads you eastward towards Forest Park.
Once at Forest Park, I recommend taking their bike trails to the left clockwise around the park.
Once around the park, I recommend taking Pine Street through several nice neighborhoods where eventually you will run right into the St. Louis University campus.
Go through the SLU campus for about 1 mile until you reach the baseball and softball fields, then turn left and join the bike lanes along Olive Boulevard (again).
Take the Olive bike lanes eastward for about 2 miles until you reach 20th Street where you will turn right.
Go two short blocks to Chestnut Street and turn left. Enjoy the new parking protected bike lanes along Chestnut past Union Station all the way to 4th Street where you will see the Old Courthouse and the Arch.

If you want to follow the Weldon Spring to Downtown St. Louis directions, then you will have to trace it out in the opposite direction because you are starting at the Arch. My directions are from 2015, but I still think that they are the best option out there if you are starting from the Arch and not the Kirkwood train station. You can go to Google Maps, turn on the cycling layer, and see that most of my route is highly recommended. If you don't like biking on busy four lane streets, then there are a few options that eliminate the one busy stretch of Olive by Lindbergh and I-270. I can also share my Garmin map link of this route if you want to see it.

How far of a trip can we expect to St. Charles if we start at the Arch? Thank you. Also if anyone has any relevant information, please share either here or email me. Thnak you..

The route that I described first along the Mississippi Riverfront Greenway Trail is 12 miles, plus 28 miles to cross into Illinois (taking the Illinois greenway up to Alton and then back across the river to Machens), and then 13 more miles to get from Machens to St. Charles (53 miles total). The second route through the city is 26 miles to go through the city and cross the Missouri River at the Page Avenue Bridge bike crossing where you join the Katy Trail, and then you just have to ride 3 miles back east in order to reach St. Charles (about 29 miles total).