This thesis contributes four essays to the theoretical literature of Economic Growth and Development covering issues of environment, optimal taxation, demography, gender inequality, endogenous technological progress, and comparative development in variations of overlapping generations modelling. The first essay addresses tax and transfer policies to conduct a Diamond (1965) overlapping generations economy with environmental externalities to the social optimum through Pareto-improving path. The second essay studies the role of geographical and environmental conditions as well as a mechanism under which an society can be locked in a stagnation characterized by a small population, zero-education, and low level of technology. The third essay studies the comparative development across societies by considering the differences in geographical advantage for agricultural production between societies. This essay shows that the geographical advantage for agriculture helps a society to be more prosperous in the agricultural regime, but delays its timings of industrialization and demographic transition. The last essay develops a unified growth model and proposes a new mechanism linking technology, gender inequality, and fertility to explain some stylized facts during the development process. It sheds a light that the evolution from Malthusian stagnation, through the demographic transition, to modern sustained growth along with the improvement in gender equality in education (income), and an increasing female labor supply are inevitable outcomes of the development process.