Gilpin county with 150.15 sq mi
As far as square miles - Derby, Connecticut In regards to population - Union, Connecticut
In terms of population the largest is Nairobi, the smallest Lamu county. In terms of size the largest is Turkana County about 77000 km2 the smallest Mombasa
In terms of population the 4 largest counties in Colorado are:El Paso - 622,263Denver - 600,158Arapahoe - 572,003Jefferson - 534,543In terms square miles it is:Las Animas - 4,773Moffat - 4,743Weld - 3,987Mesa - 3,329
Wyandotte County is the smallest geographically at 156 square miles. For population it looks like Greeley County with 1,534 people.
The smallest county in Utah as far as land area is Davis County. Davis County has 304 square miles of land area and 329 square miles of water. The total area of the county is 634 square miles. Morgan County is the smallest in terms of total area with 611 square miles of area, 609 square miles of land and 2 square miles of water. The above figures come from the U.S. Census Bureau.
The world's smallest country in terms of area is Vatican City with just 0.17 square miles. Next in line is Monaco with 0.75 square miles.
You probably meant county not country. In that case the second smallest county in Ireland is Carlow. If you did mean country, the island of Ireland has the Republic of Ireland and Northern Ireland on it. The Republic of Ireland is bigger making it the second smallest, and Northern Ireland the smallest.
The largest is Berkeley County with 1,228 square miles.
The largest is Nye County with 18,147 square miles.
The smallest state in terms of size is Rhode Island, which covers an area of approximately 1,214 square miles.
Colorado is the 8th largest state in terms of square miles.
Rhode Island is the smallest state in the USA, with a land area of 1,044.93 square miles