This paper presents a new map of the structure of all of science, based on journal articles, including both the natural and social sciences. The map provides a bird's eye view of today's scientific landscape, allowing for the visual identification of major areas of science, their size, similarity, and interconnectedness. The map needs to be accurate on both local and global scales. This paper summarizes results on how to achieve structural accuracy. Eight alternative measures of journal similarity were applied to a data set of 7,121 journals covering over 1 million documents in the combined Science Citation and Social Science Citation Indexes. For each journal similarity measure, two-dimensional spatial layouts were generated using the force-directed graph layout tool, VxOrd. Mutual information values were calculated for each graph at different clustering levels to measure structural accuracy. The best co-citation and inter-citation maps according to local and structural accuracy were selected and presented. These maps are compared to establish robustness. The inter-citation map is used to examine linkages between disciplines. Biochemistry appears as the most interdisciplinary discipline in science. The paper discusses the importance of science maps in understanding the inputs, associations, flows, and outputs of the Science and Technology enterprise. A science map can be an ideal tool for this task if constructed correctly. Maps help us understand our environment, anticipate changes, and navigate the landscape. Disciplinary maps help managers understand their enterprise and navigate their relevant environment. It is important that a science map be as accurate as possible when used in decision-making contexts. The paper focuses on structural accuracy and characterization of the map defining the structure or backbone of science. It reviews related work, discusses data, similarity measures, and processing and analysis methods, and concludes with analytical results and a characterization of the backbone of science as it exists today.This paper presents a new map of the structure of all of science, based on journal articles, including both the natural and social sciences. The map provides a bird's eye view of today's scientific landscape, allowing for the visual identification of major areas of science, their size, similarity, and interconnectedness. The map needs to be accurate on both local and global scales. This paper summarizes results on how to achieve structural accuracy. Eight alternative measures of journal similarity were applied to a data set of 7,121 journals covering over 1 million documents in the combined Science Citation and Social Science Citation Indexes. For each journal similarity measure, two-dimensional spatial layouts were generated using the force-directed graph layout tool, VxOrd. Mutual information values were calculated for each graph at different clustering levels to measure structural accuracy. The best co-citation and inter-citation maps according to local and structural accuracy were selected and presented. These maps are compared to establish robustness. The inter-citation map is used to examine linkages between disciplines. Biochemistry appears as the most interdisciplinary discipline in science. The paper discusses the importance of science maps in understanding the inputs, associations, flows, and outputs of the Science and Technology enterprise. A science map can be an ideal tool for this task if constructed correctly. Maps help us understand our environment, anticipate changes, and navigate the landscape. Disciplinary maps help managers understand their enterprise and navigate their relevant environment. It is important that a science map be as accurate as possible when used in decision-making contexts. The paper focuses on structural accuracy and characterization of the map defining the structure or backbone of science. It reviews related work, discusses data, similarity measures, and processing and analysis methods, and concludes with analytical results and a characterization of the backbone of science as it exists today.