Chesapeake Energy Corp,the Oklahoma-based firm is the No. 1 driller in Ohio.
Rig Count Interactive Map by Baker Hughes, an energy services company.
Shale Sheet Fracking, a Youngstown Vindicator blog.
The Ohio Environmental Council, a statewide eco-group based in Columbus.
Earthjustice, a national eco-group.
People's Oil and Gas Collaborative-Ohio, a grass-roots group in Northeast Ohio.
Concerned Citizens of Medina County, a grass-roots group.
No Frack Ohio, a Columbus-based grass-roots group.
Fracking: Gas Drilling's Environmental Threat by ProPublica, an online journalism site.
Pipeline, blog from Pittsburgh Post-Gazette on Marcellus shale drilling.
Allegheny Front, environmental public radio for Western Pennsylvania.
According to the Ohio Department of Natural Resources, a total of 23 drilling companies are in pursuit of Ohio's Utica shale.
That total was as of Jan. 12 and is reflected in the companies getting state drilling permits.
Chesapeake Energy is No. 1 with 325 permits in 10 Ohio counties including Portage and Stark.
Other totals are:
Antero Resources, 11, in Monroe and Noble counties.
Anadarko, 12, in Coshocton, Guernsey, Muskingum and Noble.
Atlas Noble, 5, in Harrison.
Carrizo, 2, Guernsey.
Chevron Appalachia, 2, Harison County.
CNX Gas Co., 20, Jefferson, Mahoning, Noble, Portage, Trumbull and Tuscarawas.
Eclipse Resources, 1, Monroe.
Devon Energy, 13, Ashland, Coshocton, Knox, Guernsey, Medina, Wayne and Holmes.
EnerVest, 16, Carroll, Guernsey, Jefferson, Muskingum, Noble and Stark.
EQT Production, 1, Guernsey.
Gulfport Energy, 28, Belmont, Guernsey, Harrison.
Halcon Operating, 1, Trumbull.
Hall Drilling, 1, Monroe.
Hess Ohio Resources, 15, Belmont, Guernsey, Harrison and Jefferson.
HG Energy, 16, Monroe.
Hilcorp Energy, 2, Columbiana and Mahoning.
Mountaineer Keystone, 7, Portage.
Petroleum Development Corp., 4, Guernsey.
R.E. Gas Development, 8, Carroll and Noble.
Sierra Resources, 3, Carroll, Columbiana and Tuscarawas.
Swepi, 1, Columbiana.
XTO, 4, Belmont and Monroe.
In all, that's 498 permits.