coming from St. Joseph, MO. how is the best way to get to the park?

I 29 north , 80 west would be quickest way in my view, use Google maps it will let you know traffic and such.

Shared route From St Joseph to Eugene T. Mahoney State Park via I-29 N. 2 hr 9 min (139 mi) 2 hr 9 min in current traffic 1. Head west on Francis St toward N 10th St 2. Turn left onto the I-229 N/US-59 N ramp 3. Merge onto I-229 N/US-59 N 4. Use the left lane to take exit 14C for I-29 N toward Council Bluffs 5. Take exit 10 for IA-2 toward Sidney/Nebr City 6. Turn left onto IA-2 W 7. Take the NE-50 exit toward Syracuse 8. Turn right onto NE-50 N 9. Turn left onto NE-66 W 10. Turn right 11. Arrive at location: Eugene T. Mahoney State Park For the best route in current traffic visit https://goo.gl/maps/f2pVGF9aMt92

I80 all the way is the quickest

Go to Omaha, take I 80 west to the Mahoney State Park exit, turn right, take 2nd right into park or follow Google map directions.

Google maps will tell you.