Group I counties:
001 - Adams
003 - Antelope
005 - Arthur
007 - Banner
009 - Blaine
011 - Boone
013 - Box Butte
015 - Boyd
017 - Brown
019 - Buffalo
021 - Burt
023 - Butler
025 - Cass
027 - Cedar
029 - Chase
031 - Cherry
033 - Cheyenne
035 - Clay
037 - Colfax
039 - Cuming
041 - Custer
X01 - Dakota
045 - Dawes
047 - Dawson
049 - Deuel
051 - Dixon
053 - Dodge
055 - Douglas
057 - Dundy
059 - Fillmore
061 - Franklin
063 - Frontier
065 - Furnas
067 - Gage
069 - Garden
071 - Garfield
073 - Gosper
075 - Grant
077 - Greeley
079 - Hall
081 - Hamilton
083 - Harlan
085 - Hayes
087 - Hitchcock
089 - Holt
091 - Hooker
093 - Howard
095 - Jefferson
097 - Johnson
099 - Kearney
101 - Keith
103 - Keya Paha
105 - Kimball
107 - Knox
109 - Lancaster
111 - Lincoln
113 - Logan
115 - Loup
117 - Madison
119 - McPherson
121 - Merrick
123 - Morrill
125 - Nance
127 - Nemaha
129 - Nuckolls
X03 - Otoe
133 - Pawnee
135 - Perkins
137 - Phelps
141 - Pierce
139 - Platte
143 - Polk
145 - Red Willow
147 - Richardson
149 - Rock
151 - Saline
153 - Sarpy
155 - Saunders
157 - Scotts Bluff
159 - Seward
161 - Sheridan
163 - Sherman
165 - Sioux
167 - Stanton
169 - Thayer
171 - Thomas
173 - Thurston
175 - Valley
177 - Washington
179 - Wayne
181 - Webster
183 - Wheeler
185 - York
Group II counties:
001 - Adams
003 - Antelope
005 - Arthur
007 - Banner
009 - Blaine
011 - Boone
013 - Box Butte
015 - Boyd
017 - Brown
019 - Buffalo
021 - Burt
023 - Butler
025 - Cass
027 - Cedar
029 - Chase
031 - Cherry
033 - Cheyenne
035 - Clay
037 - Colfax
039 - Cuming
041 - Custer
X01 - Dakota
045 - Dawes
047 - Dawson
049 - Deuel
051 - Dixon
053 - Dodge
055 - Douglas
057 - Dundy
059 - Fillmore
061 - Franklin
063 - Frontier
065 - Furnas
067 - Gage
069 - Garden
071 - Garfield
073 - Gosper
075 - Grant
077 - Greeley
079 - Hall
081 - Hamilton
083 - Harlan
085 - Hayes
087 - Hitchcock
089 - Holt
091 - Hooker
093 - Howard
095 - Jefferson
097 - Johnson
099 - Kearney
101 - Keith
103 - Keya Paha
105 - Kimball
107 - Knox
109 - Lancaster
111 - Lincoln
113 - Logan
115 - Loup
117 - Madison
119 - McPherson
121 - Merrick
123 - Morrill
125 - Nance
127 - Nemaha
129 - Nuckolls
X03 - Otoe
133 - Pawnee
135 - Perkins
137 - Phelps
141 - Pierce
139 - Platte
143 - Polk
145 - Red Willow
147 - Richardson
149 - Rock
151 - Saline
153 - Sarpy
155 - Saunders
157 - Scotts Bluff
159 - Seward
161 - Sheridan
163 - Sherman
165 - Sioux
167 - Stanton
169 - Thayer
171 - Thomas
173 - Thurston
175 - Valley
177 - Washington
179 - Wayne
181 - Webster
183 - Wheeler
185 - York
Group III counties:
001 - Adams
003 - Antelope
005 - Arthur
007 - Banner
009 - Blaine
011 - Boone
013 - Box Butte
015 - Boyd
017 - Brown
019 - Buffalo
021 - Burt
023 - Butler
025 - Cass
027 - Cedar
029 - Chase
031 - Cherry
033 - Cheyenne
035 - Clay
037 - Colfax
039 - Cuming
041 - Custer
X01 - Dakota
045 - Dawes
047 - Dawson
049 - Deuel
051 - Dixon
053 - Dodge
055 - Douglas
057 - Dundy
059 - Fillmore
061 - Franklin
063 - Frontier
065 - Furnas
067 - Gage
069 - Garden
071 - Garfield
073 - Gosper
075 - Grant
077 - Greeley
079 - Hall
081 - Hamilton
083 - Harlan
085 - Hayes
087 - Hitchcock
089 - Holt
091 - Hooker
093 - Howard
095 - Jefferson
097 - Johnson
099 - Kearney
101 - Keith
103 - Keya Paha
105 - Kimball
107 - Knox
109 - Lancaster
111 - Lincoln
113 - Logan
115 - Loup
117 - Madison
119 - McPherson
121 - Merrick
123 - Morrill
125 - Nance
127 - Nemaha
129 - Nuckolls
X03 - Otoe
133 - Pawnee
135 - Perkins
137 - Phelps
141 - Pierce
139 - Platte
143 - Polk
145 - Red Willow
147 - Richardson
149 - Rock
151 - Saline
153 - Sarpy
155 - Saunders
157 - Scotts Bluff
159 - Seward
161 - Sheridan
163 - Sherman
165 - Sioux
167 - Stanton
169 - Thayer
171 - Thomas
173 - Thurston
175 - Valley
177 - Washington
179 - Wayne
181 - Webster
183 - Wheeler
185 - York