The old courthouse was the first permanent building on the square downtown. This original gothic style building was built in 1876 and stones were quarried three miles from town for the construction. In 1927 the building was remodelled to how it looks today. There is a story that a ghost of a lady in white has been seen at night looking out of the window. This lady reportedly was supposed to have hung herself back in 1896.
The Old Collin County Courthouse is smack dab in the middle of downtown McKinney. This version was finished in 1876 - the courthouse that stood on the same spot before had been made of pine logs. Unfortunately, the building is now closed to the public - which means no tours. But, there's talk of renovating the interior - sooner or later the place will probably become a museum of some sort.
courhouse and McKinney history: http://www24.brinkster.com/mckinneymall/mckinney_info/mckinney_history.htm